UNDERSTANDING PACKET TERMS MADE EASY
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The
first need of the newcomer is an understanding of the jargon or buzz-words and
terms associated with packet radio. The second need is directly related to the
"how do we put a system together"?
To
these ends and in that same manner, I wish to address this glossary. I will
first give a synopsis of the packet station requirements and configuration
procedures. Later we will study the single word, or letter groups that are
called; "acronyms and mnemonics."
Here
is what I hope we will achieve; When you read this section, you will begin to
learn about Packet in a new way, and with more understanding. The rest of the
learning process is easy because the nature of Packet is one that allows
"learning by osmosis."
After
completing this addendum, you will have a better understanding of the dialog of
Packet Radio, and of the terms used throughout this book.
You
will discover that you have developed a more fluent understanding of the packet
radio and the terms associated with your "hobby". In addition, you
will be able to put your packet station on the air with less difficulty than
those who have not studied this kind of material.
You
will become the expert of packet "jargon" in a very short time. The
added benefit, is an increased knowledge about the subject, and you will be on
the air with the best of us who enjoy the most advanced communications mode to
date.
A
AAR
Automatic
Alternate Routing.
ABAUD
(In
some terminal node controllers is called "TBAUD") Data speed between
the computer terminal and the TNC.
ABSOLUTE
DELAY
The
actual time taken for a signal to transit a Packet signal from end to end;
affected by the actual circuit length and the "propagation constants"
of the type of medium used.
ACK
Acknowledgment
from target Packet station receiving an error-free Packet from the station which
sent the original Packet of information. The "acknowledge" character
in many data codes, used most commonly for an affirmative response of correct
receipt. The "ACK" lets the sending station know if it should send
another packet, or resend a missed or "nack" (defective) Packet. ACK
is used most commonly for an affirmative response of correct receipt. (Compare
to NACK).
ADAPTIVE
ROUTING
In
data networks, routing algorithms capable of adjusting message routes in
response to changes in traffic patterns or transmission channel failures. eg;
Alternate routes in the X-1J/X2 nodes.
ADDRESS
In
Packet Radio networks, the distinct identifier of a destination node or station.
AEA
Advanced
Electronics Applications Inc. AEA designs, manufactures and markets a wide range
of amateur packet products as well as other amateur related items. The AEA
products are now marketed by "TIMEWAVE" corp.
AFSK
Audio
Frequency-Shift Keying. A method of digital modulation. This is a mechanism for
sending digital information over a radio. A signal 0 (zero) is sent using one
tone while the signal 1 (one) is sent using a different tone. This is the
mechanism used by telephone modems and packet radio modems. When associated with
VHF Packet, the audio frequency-shift is usually 1000 Hz. A 0 (zero) is one tone
while a 1 (one) is a different tone.
AFT
Amateur
Framing Technique. This is the protocol used by ROSE switches on an RS-232 LAN.
ALGORITHM
a
prescribed set of steps that implement a function or task; a mathematical
solution.
ALIAS
The
"alias" is normally used to identify the location of a digipeater.
Many "nodes" are given the local airport identifier or the
abbreviation for the city or state of origin.
ie;
The alias of Lynchburg, Virginia SEDAN node is "LVA."
The
"alias" also eliminates the need to type in long call signs and SSID.
ALOHA
NET
An
early (1975) packet radio experiment conducted by the University of Hawaii. The
Aloha net is known for it's performance definitions for packet systems which
have hidden transmitters.
ALTERNATE
ROUTE
A
secondary communications path used to reach a destination if the primary path is
unavailable.
ALTERNATE
USE
The
ability to use communications transmission facilities for multiple applications
- voice or data being the most common example.
AMBIENT
NOISE
Constant
noise present in all forms of telecommunications paths; a condition that most
Packet communications networks operate with.
AMERICAN
NATIONAL STANDARDS INSTITUTE (ANSI) br
Official
repository of standards for the United States of America.
Example:
ASCII data communications code is ANSI C.64 and CCITT International Telegraph
Alphabet Number 5, with only the smallest variation in a few definitions.
AMERICAN
WIRE GAUGE (AWG)
Descriptive
of the diameter of wire conductors, particularly in twisted pair cabling; has
effect on the transmission capacity and distance a given wire can offer.
AMPLITUDE
Magnitude
or size; voltage or power of an electronic signal.
AMPLITUDE
MODULATION (AM)
Modifying
a "carrier" signal by varying its instantaneous power to represent the
information it carries; most commonly called "AM."
AMRAD
Amateur
radio Research And Development corporation, is a non-profit group based in
Virginia that has promoted many of the present day guidelines and practices that
affect Packet Radio. AMRAD is one of the first organizations that was
established to advance Packet Radio communications.
AMTEX
AMtor
TEXt. A bulletin broadcasting system used by AMTOR bulletin stations like W1AW.
Similar to the US Coast Guard NAVTEX system of naval advisories.
AMTOR
AMateur
Teleprinting Over Radio. An improved method of RTTY that uses some forms of
error recognition and correction to improve copy. Sort of a very simple basic
form of packet using 3 character groups. AMTOR uses a limited character set
(Capitol letters, numbers and a couple of controls like CR/LF - similar to the
Baudot set). AMTOR is normally used on HF frequencies. AMTOR is modeled on a
commercial protocol called SITOR. (See ARQ, FEC, SITOR , FACTOR, RTTY, Baudot)
ANALOG
SIGNAL
A
signal in a form that varies in step with the actual transmitted information.
The retransmitted analog signal is not always an exact replica of the input.
ANALOG
TRANSMISSION
Communications
by transmission of continuously varying representations of the input signal, as
compared to coded words in digital transmission.
ANSI
American
National Standards Institute. A US organization that sets standards for almost
any manmade tangible item .. from horseshoes to hand-grenades. E.g. nuts, bolts,
tires, computers...etc. (See ISO)
APLink
Amtor
Packet Link. An AMTOR BBS program written by Vic W5SMM and used on an IBM PC to
operate an AMTOR mailbox and gateway between the packet BBS network and
international AMTOR links.
APPLICATION
LAYER
The
topmost, visible to the user, presentation of a communications network; the user
level of Packet Radio (AX.25) is Level 2.
ARPA
SUITE
The
set of protocols standardized by the Advanced Research Projects Agency of the US
Dept. of Defense. Includes TCP and IP as elements, but leaves the lower levels (subnetwork
and down) deliberately unspecified. The ARPA suite can be run on top of multiple
subnet- works, concentrating them into a single Internet.
ARQ
Telegraphic
code signal for "Automatic Repeat Request," a time-honored method of
telegraphic error correction upon which most data transmission error correction
is based. An error correction technique in AMTOR where the receiving station
sends 1 character ACK/NAK response to each AMTOR group sent. (See AMTOR, ACK,
NAK, FEC, handshalzing). ARQ receivers check for errors and initiate an order to
retransmit data blocks determined to be corrupted in transmission.
ASCII
American
Standard Code for Information Interchange. The ASCII 7 bit code with an eighth
parity bit for error checking, it represents 128 characters, including 32
control characters. The most common code used for asynchronous data transmission
by minicomputers and personal computers.
Also
known as the ANSI standard X3.4 1977. The ASCII code set is used in almost all
computers and the peripherals. ASCII is the basis of most information which is
transmitted by amateur packet stations.
ASLIP
Asynchronous
Serial Line Protocol (usually just called SLIP). A technique for encoding IP
datagrams so they can be sent across ordinary asynchronous modems and
communications hardware.
ASR
Telegraphic
name for an "Automatic Send/Receive" terminal station, typically one
that has storage for outbound messages and holds them until called upon by the
communications network to send. Compare to "TNC or DIGIPEATER."
ASYNCHRONOUS
Occurring
without central control or in an unpredictable time interval between successive
elements; the typical mode of telegraphy, minicomputers and personal computers;
requires s transmission of "start" and "stop" bits to
provide decoding synchronization at the receiver.
ATTENUATION
Term
denoting a decrease in power between that transmitted and that received due to
loss through equipment, lines, or other transmission devices. Usually expressed
as a ratio in dB (decibels). - Synonym: Loss; Antonym: Gain
AUDIT
TRAIL
The
list of headers (R: lines) attached to every BBS message that is used to trace
the path the message assumed from its originating BBS.
AUTOMATIC
ALTERNATE ROUTING (AAR)
Provision
or function in a network to obtain a connection via secondary routes between two
locations without need for user intervention. Compare to TheNET X-1J4 nodes.
AUTOFORWARD
Many
bulletin board and mail server programs (BBS) are capable of passing messages to
each other. The process of a bulletin board recognizing that it has
mail
to go to another bulletin board, connecting to another board and then sending
the traffic is called Autoforwarding. This allows packet users to send mail in a
non real time fashion anywhere on the planet where compatible Packet BBSs
exists.
AUTOMATIC
ANSWER
-
A function providing for a transmission control unit or station to automatically
detect a connection and responding with a preset line of "connect
text". Most commonly associated with personal mailboxes within the firmware
of the TNC for Packet Radio use.
AUTOMATIC
BAUD RATE DETECTION (AUTOBAUD)
A
function of data TDM's (See "Time Division Multiplex") to sense and
self-adjust to the data rate of connections made to one of the TDM's ports.
Typically used in modern MoDems and when initializing many Packet Radio TNC for
the first time.
AUTOMATIC
ROUTE OPTIMIZATION
In
some Packet radio systems, this feature may denote added ability to adjust
routing depending on traffic load or time of day. Some route adjustments may be
accomplished by the System Node Operator (SNO) by locking routes to neighbor
nodes at a higher quality number than that set in the nodes third parameter.
AUTOMATIC
ROUTING
A
means of internode data and traffic positioning through several network nodes
that enables the fastest usable routing. This routing is usually determined by
the node, however the node system operator may influence the routing by
installing fixed or locked nodes and/or routes.
AUTOMATIC
TRUNK
A
node connection whose destination is predetermined by the node sysop. Most
commonly used feature of the X-1J4 TheNET firmware. This enables or initiates a
connect to a programmed destination node.
AX.25
The
user level of Packet Radio (AX.25) is Level 2. The protocol or data
"envelope" set aside for use in Amateur Packet Radio. The envelope
contains the callsign of the originating station, the callsign of the target
Packet station, synchronizing, addressing, control and error-checking
characters. It is transmitted as a single "frame" and designated as an
AX.25 Packet. AX.25 amateur packet radio link level protocol that borrows the
link layer from X.25 (also known as "LAPB"), modifies it, and tacks a
datagram-style address/routing header on front
B
BACKBONE
A
backbone is a system of links where nodes may communicate without interfering
with or being interfered with by local access, and where data may be passed in a
fashion and with hardware that is optimized for passing data, rather than
optimized for user stations.
BACKBONE
FACILITIES
A
transmission facility designed to interconnect tributary facilities from
clusters of dispersed users or nodes. A "backbone" can range from a
single network like the SouthEast Digital Association Networks (SEDAN) to an
intercontinental Packet Radio network.
BALUN
A
form of impedance-matching transformer primarily to match radio antennas to
unbalanced coax.
BAND
In
analog transmission, the range of frequencies between two defined limits.
BASEBAND
In
Packet Radio communications, the total frequency band occupied by the aggregate
of all the data signals used to modulate a carrier. In LANs, a physical
transmission path using direct digital signaling, usually at a rate stated in
megabits per second.
BATTERY
BACKUP
Usually
associated with the internal TNC lithium cell used to maintain the information
stored in the TNC's RAM. This battery backup holds the "user
configuration" while the TNC is OFF. Other forms of battery backup is the
power source that supplies power to a station or site when utility power is
removed or fails. This power source is sometimes called "emergency or
auxiliary power."
BAUD
A
unit of signaling speed. The speed in Baud is the number of discrete conditions
or signal elements per second. If each signal event represents only one bit
condition, then Baud is the same as bits per second. Baud does NOT equal bits
per second. Another method of expressing "baud" is; The unit of
digital signal speed, equal to the number of events per second.
BAUDOT
A
5 bit code used in RTTY communications. Named after J. Baudot, an early French
inventor of telegraphic instruments. Compare with: ASCII which is an 8 bit code
capable of coding 256 characters instead of 32 for baudot.
BAYCOM
A
simple modem and software package designed and supported by DL8MBT, DG3RBU and
the Baycom group in Germany. Early versions were shareware. Recent versions are
now marketed as a commercial product.
BBS
Bulletin
Board System. This is a server which is accessed by packet stations to be a
repository for messages and files. These messages and files can be accessed by a
packet operator who connects to the BBS. BBS also have a capability called
Forwarding which may be used to transfer files between BBSs. (See autoforward)
BEAM
A
directional antenna. Beams are usually made of aluminum and are constructed from
a horizontal length of tubing having between 4 and 16 1/2 wave length aluminum
elements. Beams for packet radio usually cost between $50 and $100. The key
features of a beam are:
1.
Directionality
2.
Gain.
In
this case gain means this is because less power and signal is wasted in the
direction away from where the beam is pointed. The main lobe power is
concentrated in the direction the beam is pointed.
BER
Bit
Error Rate; The average number of errors that occur per fixed amount of
data-bits sent. This number is usually stated as; error(s) per million bits.
Another way to express BER is the ratio between the number of bits transmitted
and the number received in error on a transmission link. This is the process
most often used as a measure of quality for data links.
BERT
Bit
Error Rate Test/testing; The process of testing or proving the bit error rate(s).
The device used to determine the BER is called a "BERT" meter and may
be left in the digital stream without affecting the data being measured. The
test method for digital links uses a psuedorandom repeating sequence of bits,
comparing the received pattern with the known transmitted pattern for errors.
Computing
the gross errors over a fixed test interval. Error rate is stated in scientific
notation as the number of errored bits per hundred thousand, million, ten
million, or hundred million. Minimum acceptable error rate for voice channel
data operations is one errored bit per 100,000 transmitted.
BETA
TEST
Beta
test is the pre-release testing of hardware or software with selected typical
customers to find out if there are any bugs or problems before releasing it to
the general public.
BID
Bulleting
Identification; Usually applied to BBS bulletins that are forwarded across a
Packet network. The purpose is to identify or track the bulletin (--e.g.,
source).
BINARY
A
two state numbering system represented by the 0 (zero) and 1 (one). A binary
digit is called a "bit". Digital data is represented by a one or zero
bit when used in packet communications.
BINARY
CODED DECIMAL (BCD)
A
binary-coded notation in which each decimal digit of a number is expressed in
binary form; Example: 23 decimal is 10111 in binary, and 0010 0011 in BCD.
BINARY
CODED DECIMAL INTERCHANGE CODE (BCDIC)
7-bit
implementation of a code for synchronous data communications. In essence BCDIC
has been replaced by EBCDIC at this point in time.
BIPOLAR
In
communications, the predominant line signaling method used for baseband digital;
zero and one values are represented by positive and negative voltages
respectively, as in " polar " telegraph circuits. In high-speed
integrated circuit electronics, a similar technique used for transmission within
a CMOS chip is typified by the Bipolar CMOS .
BIT
Notation
for a binary digit. The smallest unit of digital information. The bit can
represent a choice of a one or zero (mark or space) in digital communications. A
contraction of the words," binary digit."
BIT
DURATION
The
time taken for one bit to pass a point on a transmission link. Also called: bit
length, bit time, bit interval, bit period, bit interval .
BIT
ORIENTED
Descriptive
of data communications protocols using a control byte rather than embedded
control characters or control messages as well as having a high degree of
transparency to codes used for messages. Typified by IBM's SDLC and the CCITT's
HDLC of X.25 packet networks.
BITS
PER SECOND (BPS, b/s)
Basic
unit of measurement for raw transmission throughput on a link. Often stated in
kilobits, megabits, or gigabits.
BIT-STUFFING
A
technique used to prevent confusion between any 111111 bit pattern in the data
and the flag character (01111110) used to delimit the start and end of each
frame in the packet.
BLOCK
In
Packet Radio communications, a string of data set into an "envelope"
of synchronizing, addressing, control and error-checking characters transmitted
as an entity. Equivalent to "frames" (MAXFRAME) in AX.25 Packet Radio
systems.
BLOCK
ERROR RATE (BLER)
The
ratio of number of blocks transmitted to the number of blocks containing errors;
a user-oriented measure of data transmission quality. Synonomous with
"frame error rate" in digital communications line systems.
BLOCK
LENGTH
Measure
of the size of a transmission block in data communications; stated in
characters, records, language words, computer words, characters; but rarely
bits.
BOOT
Boot,
reboot, and system boot, refer to a "cold start" of a computer or
related devices.
BOOTSTRAP
LOADER
In
personal computers it is the sequence that searches predetermined disks for a
Command Interpreter program, then a Configure System (CONFIG.SYS) or and
AUTOEXEC.BAT file.
BPQ
A
node or packet switch software written by John G8BPQ that creates a multiport
node on an IBM PC or clone. Popular with BBS operators to provide multiconnected
BBS services with several ports to both LAN and Backbone ports.
BPS
Bits
per second. The rate at which binary data is transferred on a circuit. See also
baud, data rate, transfer rate.
BREAK
In
Packet and data transmission systems, a timed interruption of about 300
milliseconds, often intended to interrupt a distant transmitting station.
BREAKOUT
NODE
This
is a node that is capable of handling multiple links. In many cases packet nodes
have been installed in places where several radios or backbone links are not
allowed, such as on high mountains of great commercial value. A breakout node
holds no special purpose except it is a node that has proven to be expandable.
BRIDGE
In
Packet networks, a set of nodes (2 or more) may be interfaced to form a bridge
or gateway (node-stack) between frequencies or baud rates. In LANs, an
electronic device providing a logical connection path between two LAN segments.
BROADCAST
In
telecommunications, a transmission mode in which every message is transmitted to
all stations. Similar to the broadcast that is used in conference or converse
nodes.
BSQ
A
digital/data communications protocol used to send binary files via packet radio.
BUFFER
A
storage area or device (normally in RAM) where data overflow is contained until
RAM or disk space can be made available for storage. The buffer is mainly used
to hold data while it is being transferred from one computer to another.
-e.g.,
A temporary storage medium to permit some difference in the capacity of two data
devices to emit and accept data from each other.
BUG
Computer
term for an error or mistake causing a processing delay or stoppage.
BULLETIN
BOARD SYSTEM (BBS,
A
communicating computer equipped so as to provide informational messages, file
storage and transfer and a degree of message exchange to allow use by Packet
Radio users. e.g MBL, FBB, AA4RE etc BBS programs.
BURST
In
data communications, an event containing a number of elements, as in a burst of
errors. In other communications, a term descriptive of the intermittent
occurrence of errors.
BUS
A
common physical conductor, to which several units of compatible type are
connected in parallel, sharing use of the bus.
BUS
INTERFACE UNIT (BIU)
IN
LANs, the device furnishing direct connection of a DTE to the LAN bus.
BUSY
HOURS
Prime
time, that period of hours when connections are most in demand in a Packet Radio
network.
BYPASS
The
connection of two customer locations circumventing use of the Packet Switched
Network, particularly locally.
BYTE
In
computers, a very specifically-sized unit containing 8 bits for the computer to
operate on. Sometimes called a "word" in computer systems.
C
C
BAND
A
portion of the electromagnetic spectrum used heavily microwave and satellite
transmission. Frequencies in the region of 4 to 6 Gigahertz.
CALLBOOK
SERVER
This
is a network server whose function is to allow stations to access, in real time,
Amateur radio callbook information. The servers are operated both stand-alone
and as part of a BBS or DxCluster.
CARRIAGE
RETURN
On
a mechanical typewriter the motion of pressing or pushing the carriage return
lever to the left until it stops, to allow a new line to be type on the paper
supported by the carriage. On modern computer keyboards the carriage return key
still exists and is either is labeled {Enter}, Return, or Carriage Return.
The
function of the carriage return key is to instruct the computer or remote device
that the end of a typed line has been reached. On a terminal or computer
emulating a terminal when the carriage return is pressed. In a computer, the
binary number 00001101 is generated to cause a carriage return to be sent.
CARRIER
A
signal of known characteristics that is modulated to carry information. The
receiver, knowing the expected characteristics of the carrier, can extract the
information from it. However, noise or unintended changes to the carrier will,
of course be also interpreted as part of the information.
CARRIER
SENSE MULTIPLE ACCESS (CSMA)
A
LAN access method in which stations listen to see if the transmission path is
clear before starting to transmit. This is the method used in the AX.25 Terminal
Node Controller (TNC).
CARRIER
SENSE MULTIPLE ACCESS/COLLISION DETECTION (CSMA/CD)
A
refinement of CSMA in which stations can identify not only an idle channel, but
if a collision has just occurred, in which case they wait additional time to
give the preceding stations access priority to clear their traffic.
CARRIER
SYSTEM
A
transmission system capable of providing multiple communications channels over a
single physical path.
CATHODE
RAY TUBE (CRT)
A
common form of visual display for data terminals, similar to a television
picture tube.
CCIR
Comite
Consultatif Internationale des Radio, a major constituent of the International
Telecommunications Union issuing both Radio Regulations and Recommendations for
all uses of radio transmission.
CCITT
Committe
Consultatif Internationale des Telephones et Telegraphes, or Consultative
Committee of the International Telephone and Telegraph. An international
counterpart to the Electronic Industries Association in Washington, D.C.
EIA
standard RS-232 and CCITT V.24 are similar. A major constituent of the
International Telecommunications Union (ITU) that sets standards for the
operation of telecommunications services across international boundaries. Some
CCITT standards are adopted for use in the USA.
CELLULAR
Broken
up into small areas, or cells(similar to the "honey-comb"). If a
packet network is broken up into two kinds of links, user and backbone, only
user links would be omni-directional. The coverage of a single user port might
be thought of as a cell. The area covered by a cell would be best if there were
a limited number of users in the cell. A suggested area of coverage is 50 total
packet users or ten maximum on line at once. The cell size varies depending on
what area the cell is in.
CHANNEL
A
communications transmission path via any transmission medium - wire, radio,
optical fiber etc.
CHANNELIZATION
Division
of a larger capacity channel into a number of smaller channels for use by
multiple functions.
CHARACTER
a
unit of typographic information, usually variable as part of a language. Because
data is handled and transferred as a series of characters,the term also can mean
one bit pattern in a specific data code. Often referred to as a "word"
in the computer programming sense. In their nature, these characters are 8-bit
"words" conveying the instantaneous amplitude level of their
transported signal.
CHARACTER
ORIENTED
Descriptive
of a Packet Radio communications protocol or transmission procedure that has
control information transmitted in the form of special bytes called control
characters
CHAT
NODE
See
conference node. See Convers node.
CHOKE/UNCHOKE
When
a computer is unable to process data as fast as another computer is sending it
the receiving computer may instruct the sending computer to stop sending the
data. This condition sometimes occurs in a node network running theNET node
code. An "Unchoke" packet is sent periodically to clear the nodes of a
choke condition.
CIRCUIT
As
applied to Packet Radio. A path including any needed supervisory and signaling
or conditioning equipment for the transmission of digital signals. In a TheNET
network a circuit is an assigned connection between two nodes. Each of the two
nodes has information to the effect that the circuit exists. The two nodes also
have a routing table from which the first element on the path to the other node
may be realized but the two nodes do not know all of the intervening nodes. The
circuit exists until the destination user or server or the originating user or
server disconnects, or until one of the two nodes decides that data cannot be
sent any longer (due to L4 retry time-out or unchoke failure) or if no data is
passed across the circuit during the time set by the no activity time-out. In
the recommended network the L4 retry time-out is 5 minutes times 2 retries and
the no activity time-out is two hours.
CLOCKING
Repetitive,
regularly timed signals used to control Packetized transmissions.
CMD:
An
on screen prompt which is displayed by the TNC. This prompt informs the user
that the TNC is in the "command" mode.
COAXIAL
CABLE
A
cable in which one conductor surrounds the other. The electromagnetic wave
travels between the grounded outer shield and the central conductor. Coaxials
can carry much wider bandwidth and higher frequencies than wire pairs. Where the
maximum frequency capable on twisted pair wiring is about 10 megahertz and for
short distances, coaxial cable readily carries several hundred megahertz for
thousands feet.
COLLISION
Simultaneous
transmissions on a Packet LAN that interferes with each other in a
contention-based access scheme. Occurs when two or more terminal node
controllers (TNC) attempt to transmit at nearly the same instant.
COMMON
CONTROL SYSTEM
(A
Packet node) An automatic switching system that makes use of common equipment to
establish a connection. Once connection is made, the common control equipment is
available to establish another connection.
COMPATIBILITY
A
property in data processing and telecommunications systems permitting exchange
of information directly and in usable form. IBM compatible implies identical or
interchangeable signals and methodologies on a non-IBM PC as that of a
"true-blue" IBM PC.
COMPRESSION
In
data communications, compacting the number of bits used to represent the
information, losing the character structure while reducing the circuit time or
capacity needed to transfer the data. Decompression is then needed at the
receiving end to again render the data useful. Example; ZIPPED files.
CONFERENCE
NODE
A
node which has a similar feature to theNET X-1J+ TALK mode whereby a number of
users may connect and enter into a "round-table" discussion. This mode
is sometimes referred to as a "CONVERS NODE."
CONNECTED
The
condition that occurs when two Packet stations are described as being
"connected". The state in which the two station read only those
Packets from each other when MCON is OFF.
CONTROL
CHARACTER
A
character inserted into a data stream to notify the receiver of a special
function to perform or to identify the purpose of the data or message associated
with it. An example of a control character is the Control G. A control
"G" will ring the bell of the connected or target station.
CONTROL
MODE
The
state a TNC must be in to permit command or control actions to occur.
CONTROL
SIGNALS
Signals
passed between parts of a communications system to oversee operation and
configuration of the system.
CONTROL
C or Ctrl C
This
is used to bring a TNC to the "command" (cmd:) mode from the
"converse" or "transparent" mode. It is executed by holding
the "control" key down and pressing the "C" key. In most
TNC's it is not necessary to press after executing a Ctrl C.
CONVERSATIONAL
MODE (CHAT MODE)
Interactive
data communications carried on between Packet stations, as in data or keyboard
conversation.
COSI
Connection-oriented
Open Systems Interconnect. A project of W2VY and N2DSY to implement for amateur
packet radio use the connection-oriented protocols published by the
International Standards Organization (ISO) and the International Consultative
Committee for Telephony and Telegraphy (CCITT). (OSI protocols include both
connection-oriented and connectionless flavors, hence the inclusion of the
qualifier "connection-oriented" in the name).
CPU
The
Central Processing Unit that controls data flow and "thinking"
function within a computer. When supported by a "MATH Copressor", it
can perform computations at greater speeds.
CR
(CARRIAGE RETURN or [Enter])
A
control character causing the print or display position to move to the first
position on the line, drawn from the typewriter and teleprinter function with
similar action.
CROSS
CONNECTION (X-CONNECT)
In
Packet Radio communications systems, a bit stream addressed between two ports of
a node or routing unit. See also "digital cross-connect as in theNET
X-1J4."
CROSS
TALK
Unwanted
energy (speech, tone or digital pulses) transferred from one transmission path
to another. Comprises part of the "noise" observed on analog
communications circuits.
CYCLIC
REDUNDANCY CHECK (CRC)
A
powerful error checking method for data and digital communications. The
transmitting terminal computes a numeric value representative of the number of
marking bits in the associated block of data and sends that value to the
receiver, where the number is recomputed to compare against the block as
received. Values of CRC-8 and CRC-16 are adequate for most AX.25 messages, while
CRC-32 is needed mainly for very long blocks of tens of thousands of characters
as noted in Internet type environments.
D
DATA
Multiple
units of information. Singular is " datum ".
DATA
CIRCUIT
Packet
Radio Communications channels provided specifically for the exchange of data as
compared to voice or other information forms.
DATA
COMMUNICATIONS EQUIPMENT (DCE)
The
device or TNC which provides signal conversion so that data communications can
be established, maintained, and discontinued. Some DCE are controlled through
local or remote software commands.
Standards
body term for devices that perform signal conversion at the extremities of a
data circuit. A data set (modem) or a CSU are common examples of a DCE. Contrast
to DTE.
DATA
ENCRYPTION STANDARD (DES)
A
cryptographic standard defined by the National Institute of Science and
Technology (NIST) for the general public to encrypt and decrypt digital and data
transmissions.
DataEngine
A
TNC manufactured and marketed by Kantronics. The DataEngine has two HDLC radio
ports and one serial port. The modem are plugged in and provide a usuable on-air
data-rate from 300 to 19,2 Kbps.
DATA
RATE
The
basic rate at which data is transferred on a circuit. Often referred to as
"baud rate." A more correct statement is; bits per second or bps. (See
baud, bps)
DATA
SET
A
telephone industry name for a modem.
DATA
LINK
A
serial data communications pathway, generally between two adjacent nodes without
an intervening node.
DATA
LINK CONTROL
Synonomous
with link layer data protocols related to AX.25 Packet Radio. The second layer
of the ISO Reference Model for Open Systems Interconnection (OSI).
DATA
TERMINAL
A
station in a system capable of sending and/or receiving data signals.
DATA
TERMINAL EQUIPMENT
(DTE)
The standards-body term for a computer, user terminal, workstation or personal
computer used for data communications. Data Terminal Equipment is another name
for the computer used to send and receive data in digital form at its comport
(I/O) port to and from a terminal node controller (TNC).
DB-9P
and DB-9S
Electronics
Industries Association's recommended connector for use with RS-422A standard.
DB25P
and DB25S
The
connectors which will support all 25 of the RS-232 signals. Recommended by the
EIA.
DECIBEL
(DB)
The
logarithmic unit or measure of a ratio between two powers, P1 and P2.
The
equation is: db = 10 log10 P2/P1
BELOW
ARE SOME OF THE MNEMONICS ASSOCIATED WITH "DECIBEL:"
DECIBEL
(dB)
A
unit of measurement representing the logarithmic ratio of two voltages, currents
or power levels; used in telecommunications to express transmission loss or
gain; defined as one-tenth of a Bel, hence the appropriate notation is dB, shown
here.
dBm
Identifier meaning "decibels referred to one milliwatt," the common
reference point for power levels in telecommunications circuits.
dBm0
Identifier meaning "decibels referenced to one milliwatt and corrected to a
Zero dBm effective power level; "used to state the relation of a signal
level on a transmission line at other than a one-milliwatt point.
Example:
Throughout an analog system, a data set signal is to be kept 13 dB below that
for a single test tone, stated as "minus 13
dBm0
At
a carrier modulator input where test tone level is -16
dBm
A
data signal should then be 13 dB lower, or -19 dBm.
dBmp
Identifier
meaning "decibels below reference tone using psophometric (filter)
weighting," the CCITT method for noise measurements; has about 2 dB
variance from Bell methods.
dBm0p
Identifier
for CCITT psophometric-weighted noise measurements adjusted to a relative 0 dBm
transmission level point.
Example:
An absolute measurement of minus 40 dBmp noise at a carrier channel output point
would mean a signal-to-noise ratio of about 47 dBm0p exists at that point on the
circuit.
dBrn
Identifier
meaning "decibels above reference noise," the reference commonly used
being 90 decibels below one milliwatt.
dBrnC
Identifier
meaning "decibels above reference noise measured through a (filter)
weighting network approximating a " type C voice message channel;" the
common North American nomenclature for a DDD trunk channel; having a reference
of 90 decibels below one milliwatt of power.
dBrnC0
Commonly
pronounced "de-brink-o," identifier meaning "decibels above
reference noise with C message weighting adjusted for equivalence to a 0 dBm
(one milliwatt) equivalent circuit point."
Example:
A direct measurement of 49 dBrnC0 at the nominal +7 dBm output of a carrier
demodulator would mean the noise had been offset by 7 dB; thus the reading in
DBrnC0 would be 42.
DEDICATED
LINK
A
point-to-point link between two dedicated ports for the exclusive use of those
ports or nodes or for the use of stations passing through the network, using
those two nodes.
DEDICATED
PORT
This
is a port designated for a specific purpose, usually a link to another network
or application hardware. Other stations who would connect through the network
might pass across the link that uses the dedicated port. No user station would
access the dedicated port on the dedicated port's frequency.
DCE
- DTE
interfaces,
most typically RS-232 type.
DESTINATION
FIELD
Location
in a message header that contains the address of the station for which the
message is destined.
DEVIATION
The
deviation of an FM radio is the maximum change or shift in the carrier frequency
during modulation. It is usually expressed as peak deviation in kilohertz.
DIDDLE
A
term used to describe the AFSK tone shifting in some nodes and TNC.
DIGICOM
64
A
software and modem package designed to emulate a TNC on a Commodore 64 computer.
DIGIPEATER
A
store and forward "digital repeater" which will receive and transmit a
data packet on the same frequency. All amateur packet station are capable of
digital repeating in a simplex environment.
DIGITAL
SIGNAL
An
electrical signal that changes in discrete steps each representing a numerical
data value, or logic state.
DIGITAL
SIGNALING
Using
techniques that transmit information as a series of discontinuous pulsed signals
in a pattern representative of the inputted signals; requiring reconstitution at
the receiver; capable of being regenerated to minimize noise contribution in
transmission. Contrast to Analog.
DIGITAL
SWITCHING
Establishing
and maintaining a connection under stored program control, when information
passed through the switching matrix is in the form of binary encoded
information.
DIODE
MATRIX
The
device used to interface several TheNET nodes to enable communications over
their RS-232 ports. When more than two TNCs are used at a node site the diode
matrix is required for cross-connection and internode linking.
DIP
Dual
In-line Package, as applied to sub-miniature switches and monolithic integrated
circuits.
DISCRIMINATOR
In
an FM radio the discriminator is the circuit that derives audio from the IF
signal. After the discriminator the FM receiver will change the audio to remove
white noise.
DISK
DRIVE
A
disk drive is a computer accessory that stores data in the form of magnetic
impulses on a flat media that is much like an extremely high quality magnetic
recording tape. The media is on a spinning platter, like a phonograph. The media
is of two basic qualities and is called floppy or hard disks. Floppy media is
low tolerance, meaning that if the media is dented or dirty it should still
work. Floppy media can store about 200,000 characters of data per square inch.
Most floppies store less. The rate at which data can be read or written to a
floppy drive usually less than 30,000 characters of data per second.
DOVE
An
OSCAR satellite (OSCAR 17) whose full name Is Digital Orbiting Voice Encoder.
DOWNLINK
A
circuit from a node to a user, initiated by the node on command from a distant
user.
DSP
Digital
Signal Processing. A modern technique of analyzing analog signals by converting
the analog signal to a digital form and processing it with a specialized
computer circuit.
DTE
Data
Terminal Equipment. Usually refers to a terminal or computer or any equipment
that generates data.
DTR
Data
Terminal Ready. One of the RS-232 signals (pin 20 on DB-25) that indicates to
the computer or terminal of the ready-state to send data. It is associated with
the RTS (ready To Send) signal and is often used in conjunction with this signal
to enable one form of "hardware" handshaking.
DUAL
TONE MULTI-FREQUENCY (DTMF)
Also
known as Touch-Tone. A type of signaling which emits two distinct frequencies
for each indicated digit.
DUMB
TERMINAL
A
data communications euphemism indicating a DTE with no processing capability.
The data equivalent of a KSR teleprinter.
DUPLEX
Two-way
transmission. Duplex means two channel. A full duplex signal consists of two
separate channels. Both ends of the radio circuit need to have a separate
receiver and transmitter such that the receiver on each end can hear the other
station's transmitter regardless of the state of the local transmitter.
DUPLEX
DIGIPEATER
Similar
to a simplex digipeater, except that different receive and transmit frequencies
are used. Compare to: Full duplex real-time repeater which repeats received data
at exactly the same time.
DWAIT
Digipeat
WAIT. A delay in sending a packet automatically inserted by a TNC when
originating a packet. The delay starts when a packet is ready to be sent, after
the channel becomes clear. A digipeated packet is sent without waiting this
delay. Used as a collision avoidance system when digipeaters are in use.
DxCluster
A
server used by HF operators to pass information about contacts. This software,
originally written by AK1A, also operates as a database of HF related
information. A key feature of the DxCluster software is that DxClusters may
share contact information in realtime.
DYNAMIC
REROUTING
In
a network where redundancy exists in the backbone from one city to another some
types of network software allow for the network to recover automatically from
backbone hardware failure by rerouting traffic through the redundant link. This
is called "dynamic rerouting" as it can adjust dynamically to a
changing network.
E
EOC
Emergency
Operations Center. This is a term used by state governments for a state or
county government owned facility where emergency services and radio equipment is
co-located. The EOC provides for rapid deployment and coordination related to
emergency communications and associated drills.
EARTH
STATION (GROUND STATION)
A
microwave radio transmitting and receiving station working with communications
satellites.
ECHO
A
signal that has been reflected or otherwise returned with sufficient magnitude
and delay to be perceived at the far end of the circuit.
ECHO
CANCELER
A
echo removal device that operates by generating an exact opposite of any echo
signal and injecting it into the transmission path to cancel echoes. Used in
both speech telephony and in some higher-speed data modems, notably those
compliant with CCITT V.32.
ECHO
CHECK
One
method of verifying accuracy of Packet transmissions; Sometimes called
"pinging" by returning received data back to the sender as
verification and to determine path throughput level.
EDIT
Preparation
of data for a later operation; may include rearrangement or addition of data,
deletion of unwanted data, format changes, code conversion, or data compression.
EIA
RS-232
The
most common DTE serial interface by far, in use for almost 30 years, with
several revisions and additions; international equivalent: The suite of CCITT
V.24 and V.28 combined with ISO 2110.
ELECTROMAGNETIC
SPECTRUM
The
entire range of wavelengths (the inverse of frequency) of electromagnetic waves
extending from cosmic and Gamma rays down through visible light and heat to
every form of radio communications signal.
ELECTRONIC
MAIL
A
feature of LANs for transmission of computer-generated messages within a closed
community of users on the LAN.
EMULATE/EMULATION
Imitating
a system or device such that a connected device accepts the same information,
executes the same computer programs and achieves the same results as if the
emulator were one of its own kind. Most often, emulation is a downward step in
capability of the device being used, as when a personal computer is used to
emulate a mechanical teleprinter or a "dumb" terminal on a computer
network. While some degree of upward emulation is possible, it is less prevalent
in the broad view of computer communications.
ENCRYPTION
The
systematic encoding of a message or bit stream before transmission to prevent
unauthorized recipients from understanding it. The process of again rendering
the information readable is DECRYPTION.
EPROM
Erasable
Programmable Read Only Memory. This is an integrated circuit (IC) which is used
in computers, including TNCs, to permanently hold a computer program. In TNCs
all of the program is located in one EPROM. EPROMs are erasable using
ultraviolet light for between 2 and 40 minutes. EPROMs have a small lens in
their top which exposes the internal electronics. The EPROM used for The X-1J4
is usually a 27C512.
EQUALIZATION
The
procedure of compensating for fluctuation in circuit amplitude, or envelope
delay distortion.
ERLANG
A
widely-used unit of telecommunications traffic intensity, named after work of
the Danish statistician, D. K. Erlang. One Erlang is the intensity at which one
traffic path would be continuously occupied.
ERROR
In
Packet Radio communications, any unwanted change in the contents of a
transmission.
ERROR
CONTROL
In
Packet Radio communications, methods used to detect and correct transmission
channel errors.
ERROR
RATE
In
Packet Radio communications, the ratio of bits, characters, elements, blocks,
messages or files incorrectly received to the total number transmitted during a
specified time interval.
ETHERNET
Originally
the trade name for a LAN developed by Xerox Corporation; later supported by
Digital Equipment Corporation, Intel Corporation and Hewlett-Packard; now
standardized as IEEE specification 802.3.
EXTENDED
BINARY CODED DECIMAL INTERCHANGE CODE (EBCDIC)
IBM's
proprietary 8-bit code for synchronous data communications. Has numerous
variations of control character meanings.
F
FACSIMILE
(FAX)
Graphic
transmission of pictures, maps or documents via communications circuits using
terminal devices that scan documents, transforming scanned images into coded
data-like signals and reproduce likenesses of original documents at a distant
point.
FALSE
ROUTE
In
a network using TheNET software the node routing is generated automatically by
the nodes themselves. If improperly managed it is quite possible for routing to
be discovered and used by the nodes such that DX propagation paths are treated
as real paths. In this case a route may be created in the routing table that
depends on '"Lift" or enhanced propagation conditions.
When
the lift, dissappears (mostly during daylight hours) the nodes will be
helplessly trying the "false route." This condition is preventable in
a TheNET system by manually controlling the route tables to specify valid routes
to neighbor nodes.
FBBS
also FBB BBS
An
increasingly popular amateur BBS software written by by Jean-Paul F6FBB and
others.
FCC
(FEDERAL COMMUNICATIONS COMMISSION)
A
board of Presidentially-appointed commissioners empowered to regulate interstate
and international communications and all uses of radio in the United States.
Operates under the Communications Act of 1934 and several more recent laws.
Disseminates its own regulations interpreting those laws, as Title 47 of the
Code of Federal Regulations (CFR 47, 47CFR).
FCS
Frame
Check Sequence. A 16 bit (2 byte) number included with each frame in the packet
used for error checking.
FEC
Forward
Error Correction. A technique of error correction in which packets or AMTOR
groups combine the data from two or more transmissions to yield less errors.
AMTOR FEC mode, the data is sent twice and the receiving station(s) record all
known characters without resorting to an ARQ ACK/NAK transmission.
F.E.M.A.
Federal
Emergency Management Agency.
FIRMWARE
Software
stored permanently in a integrated circuit (IC) called a ROM or an EPROM.
FIBER
OPTICS (FO) "Light-Pipe"
a
technology using light as a digital information bearer. Fiber optic cables
(light pipes) are a direct replacement for conventional wire, coaxial cable and
many forms of radio, including microwave. The shortcoming of fiber optics is
when a fade occurs in it, it is of long duration and may have been caused by a
"back-hoe." Thus the term "Back-hoe fade."
FILE
SERVER (SERVER)
In
LANs, a station, often microcomputer-based, that provides the mass storage and
file access to users on the LAN. Server capabilities vary widely; some even
include ability to " gateway " to other communications means or "
bridge " to a similar nearby LAN, or even determine for users if those
functions are needed and decide the route to the user's destination, in which
case they are called " routers ".
FIRMWARE
Permanent
or semipermanent control coding built into a software-operated computer device
that operates an application program, instruction set, operating routine or
other user-oriented instructions to a computer; often resident in a ROM ( Read
Only Memory ) chip to simplify installation. FLAG - In data transmission, an
indicator of an expected event like the beginning or end of a block of data. In
CCITT standards for X.25 networks, the 8-bit character 01111110 has been
uniquely established with the name "Flag" to be used at the beginning
and end of a block.
FLOW
CONTROL
The
process that starts and stops terminal output to prevent loss of characters or
data by the receiving device. In Packet and data communications, the use of
buffering and other mechanisms that operate to avoid data loss in case the
receiver cannot keep up with the transmitter. The ASCII control characters X-ON
and X-OFF (Ctrl-Q & Ctrl-S) are frequently-used examples. They are sent in
reverse direction as an instruction for the sender to hold or continue (software
handshaking).
FLAG
A
data character (01111110) used to delimit packet (beginning and end) and to
separate multiple frames in one packet transmission. The same character is often
used during the TxDELAY to help synchronize the TNC receiver circuits at the
beginning of packets.
FM
- Frequency Modulation.
This
is a method of transferring data or voice information over a carrier signal. FM
is achieved by changing the frequency of the carrier in proportion to the wave
form of the superimposed audio signal be it voice or data. In most FM voice
applications, the FM deviation is set to 5 kHz or less. In Packet or digital FM
communications the deviation is set between 3 and 3.5 kHz. Never set Packet
Radio deviation to more than 3.5 KHz.
FORWARDING
The
transfer of files between BBSs. (See autoforward)
FORWARD
FILE
This
is the disk file on a packet bulletin board system (PBBS) that is responsible
for directing the autoforward operation. By making entries in this file the PBBS
system may select what packet paths are used to each PBBS that is forwarded to,
when each operation is per formed and what traffic is sent during each piece of
the forwarding operation. FOOTPRINT - In satellite communications, the area on
the surface of the earth that a given satellite covers; this technology has
reached a high state of development, with satellite coverages capable of being
quite shaped and tailored to the purpose of the satellite.
FORWARD
ERROR CORRECTION (FEC)
An
error-correcting technique that avoids the need for any reverse channel by
enabling self-correction of errors at the receiver. FEC operates by adding
information that enables the receiver to determine what the error was and to
substitute information that corrects the error.
FRACK
FRame
ACKnowledge delay: This is the time after a packet is transmitted by a TNC
before the TNC decides that a frame acknowledge is not going to occur. At that
point the TNC performs backoff (some TNCs + TCP/IP) and a retry. FRACK is
calculated based on the number of digipeaters that you specify in your connect
command. fr~ame
FRAME
In
AX.25 Packet Radio communications, a group of bits or characters sent serially
employing a logical unit of information between data link layer entities that
contains its own control information for addressing and error checking. Example;
see MAXFrame
FREQUENCY
The
number of complete cycles of an event (in communications typically an
alternating current signal) per unit of time; usually expressed by means of the
unit ' Hertz," named after Heinrich Hertz an early German investigator of
the properties of high-frequency alternating current waves.
FREQUENCY
DIVISION MULTIPLEXING (FDM)
The
analog method of deriving multiple transmission channels from a single physical
facility; divides of an available frequency range (bandwidth) into various
subchannels. Widely used in many formats by virtually every kind of
telecommunications technology; the " carrier systems " of telephony.
Also called Frequency Division Multiplex ; Frequency Division Mux .
FREQUENCY
RESPONSE
The
measurement of how well a transmission channel or device transports all the
frequencies sent into it; a measure of how faithfully signals are transported or
reproduced. In Bell terms, the arithmetic is reversed and the name "
amplitude response " or " amplitude variation " is used for the
same expression.
FREQUENCY
SHIFT KEYING (FSK)
When
associated with HF (300 baud) Packet, the shift is 200 Hz. One of the more basic
and durable forms of transmitting binary information; in FSK, one of the binary
states is represented by one known frequency and the other by another known
frequency. The receiver produces outputs only when one of the two known
frequencies is received in the absence of the other. Applications of FSK abound
in every form of telecommunications.
FRESNEL
ZONE
The
area in open space that must be practically free of obstructions for a microwave
radio path to function properly; some degree of Fresnel consideration is
required in the immediate vicinity of the form of microwave radio used on
satellite links.
FTP
- File Transport Protocol.
This
is a part of TCP/IP which allows a user of a TCP/IP host to request or send
files from another TCP/IP station.
FSK
- Frequency Shift Keying.
A
method of digital modulation where the carrier is switched between two distinct
frequencies. This is the technique used on HF packet.
FULL
DUPLEX (FDX)
A
circuit which allows independent transmission information in both directions
simultaneously. - Synonym: In wire telephony, 4 wire circuit.
G
G3RUH
MODEM
A
9600 bps plug-in modem for TNC-2s and other amateur TNCs. Circuitry contains
adaptable filters to adjust for bandwidth limitations in commercial radios and a
"randomizer" circuit to prevent DC offsets on modulated data. Similar
to but may not be totally compatible with K9NG modem. Believed to be compatible
with the most recent TAPR 9600 bps modem.
G8BPQ
CODE
John
Wiseman, G8BPQ, developed a Terminate-Stay-Resident program for the IBM PC and
compatibles that would imitate TheNET and allow node access for a program that
runs on the PC.
G8KBB
X1J CODE
Dave
Roberts developer of the most popular Packet Radio Networking node code in use
today. This program is a derivitive of the Nord)(Link TheNET node code but has
many enhacanced features added plus the functionality to enable allows routing
from a TheNET system directly to the Personal mailbox, Personal BBS, BBS,
DXCluster or other Packet programs running on the PC.
GAIN
Denotes
an increase in signal power in transmission from one point to another; usually
expressed in decibels. Antonym: " Loss ," a reduction in signal power.
GATEWAY
With
Packet radio, a gateway is a "bridge" that provides a means to
communicate digitally from one frequency into another or from one baud rate to
another. (see also "BRIDGE") A node-stack connection between two
different Packet networks, frequencies, baudrates or LAN. A configuration of
nodes where connectivity is available by deliberate manipulation but where
automatic end-to-end routing is not possible. This is useful for connecting two
networks together such that users and servers on one network can access users
and servers on the other network without compromising networking practices on
either.
GEOSYNCHRONOUS
ORBIT
a
position at an approximate altitude of 23,000 miles above the Equator, where a
velocity of about 1,000 miles per hour in the same direction as Earth's rotation
makes a satellite appear stationary over the Earth's surface. At such a point,
ground-based microwave antennae can remain fixed and achieve linkage with
transponders on board the satellite to produce a microwave relay between points
as much as one-third of the way around the globe, or about 8,000 miles.
GROUP
DELAY DISTORTION
Also
called envelope delay distortion. A distortion of the data signal produced when
the different frequency spectral components of the digital signal are phase
shifted by different amounts resulting in a distorted pulse shape. For best
results, it is important that radio filters, amplifiers and other components in
the communication system have a constant phase shift across their bandwidth.
This is called "flat group delay" characteristic.
H
HALF
DUPLEX
A
circuit capable of transmitting or receiving information in two directions, but
only one direction at a time; a function of both computer protocols and
transmission channels. Many computers operate only half duplex on transmission
channels capable of full duplex operation.
HAMMING
CODE
In
data transmission, a code with added redundant bits for error detection
purposes.
HANDSHAKE
The
exchange of control sequences between two locations to set up needed conditions
for communications. In the strictest sense, even the steps of dialing a
telephone call can be thought of as a "handshake sequence." On RS-232
linked devices, the RTS (or DTR) and CTS lines are used for hardware
hand-shaking or Control-S/Control-Q characters for software handshaking. On
packet radio circuits, supervisory bytes in the packet and ACK and other control
frames are used for handshaking.
HAPN
Hamilton
Area Packet Network. An active amateur packet group in Hamilton, ON best known
for the development and marketing of a 4800 bps modem (for installation in TNC-2
or clones) and plug-in TNC cards for PCs
HARDWIRE
Using
physical wire or cable directly between units of hardware equipment.
HARMONIC
An
exact multiple of a "fundamental" frequency. Examples: Second harmonic
= double the fundamental frequency; third harmonic = three times, and 12th
harmonic = one dozen times and so on. Sometimes an expression of the required
bandwidth for transmission, as in the case of binary transmission where it is
well established that a bandwidth equal to the tenth odd harmonic is needed for
accurate reception of the pulses; this means the fundamental, third, fifth,
seventh, ninth, eleventh, thirteenth, fifteenth, seventeenth, nineteenth and
twenty-first harmonics must be passed; thus a 50 bps binary pulse requires a
bandwidth of 50 x 21 or 1050 Hertz for accurate capture of the pulses ... unless
it is somehow encoded for transmission.
HARMONIC
DISTORTION
The
ratio, expressed in decibels, of the power at the fundamental frequency, to the
power of a harmonic of that fundamental. Odd harmonics, particularly third
harmonics, are especially harmful to many forms of telecommunications by both
wire and radio; as well, they are annoyingly difficult to design out of
electronic circuitry.
HBAUD
Data
speed between the TNC and the transceiver. Sometimes referred to as the
"station to station" baud rate.
HDLC
(HIGH LEVEL DATA LINK CONTROL)
A
bit-oriented international standard data link protocol used in CCITT X.25 packet
network links and influencing many others. An example is the process employed in
X.25, and AX.25 to format data into Packets. These packets of data have the
destination address, checksum count, and other necessary components added
through HDLC to help make it an error-free mode. The ISO level 2 link level
HEADER
That
portion of a message containing information for routing, handling and delivering
a message, such as address, size, priority, intermediate routing and
synchronization signals.
HEARD
OR MHEARD LIST
Monitored
& Heard; On several different packet devices, including user TNC BBSs, nodes
etc.. there exists a feature whereby a list of stations heard are recorded. This
list is called a heard list. Access to the list is different depending on the
application. Typing an M to a TheNET X-1J4 node will recover a list of recent
stations "heard" by the node.
HEXADECIMAL
A
number system based on 16, providing convenient notation of the 16 possible
combinations of half an 8-bit data processing byte; uses digits 0 through 9
followed by letters A through F to count to 16, thus two " hex "
digits can describe one byte in software. Example: ASCII letter capital
"A" has the decimal value 65 but is written as 41 in hex software
code, while small "z" has the decimal value 122 but is noted as 7A in
hex, still requiring only two digits instead of three. Hexadecimal. Numbers to
the base 16 (0-9, A-F).
Using
only two hex digits from 00 to FF, a code of 256 different characters can be
described as is done with the adaptation of ASCII used by personal computers;
the added characters beyond 128 are often called "Extended ASCII," or
"IBM graphics characters."
HOST
The
computer or massive memory storage facility where accessible data-bases are
held. These data-base are accessed by computers or terminals which are allowed
access via pre-assigned passwords or call signs. The host mode as related to
Packet is a computer or terminal attached to a TheNET node when operating in
host mode for sysop entry to the serial port. Host is also the name given the
computer that controls a TCP/IP or Internet node. (See host mode)
HOST
MODE
WB8DED
created a software package for the TAPR TNC 1 that was called Host Mode. This
package was later created for TNC 2. Some BBS programs took advantage of the
command language in Host Mode to control the TNC and to allow multiple users to
connect to the BBS at the same time. AA4RE BBS may have been the first software
to use this feature. TheNET incorporates a very small subset of the Host Mode
command set. Host Mode is used to refer to the condition where a node has a CRT
tenninal or computer plugged into it that will be used in ASCII mode (not using
networking protocol).
HOT
STANDBY/HOT SPARE
Alternate
equipment ready for immediate use if the normal equipment fails.
HTS
Hidden
Transmitter Syndrome: This describes a condition where throughput is drastically
reduced to well below the specified baud rate because a single station is able
to hear two or more stations that can't hear each other.
I
I
F - Intermediate Frequency.
The
function of a radio receiver is to convert a radio wave, which has audio on it,
to audio information to be played into a speaker or into a packet modem. The
process is often done in two steps. First the radio signal (RF or radio
frequency) is converted from the tuned frequency to a known constant frequency.
This is done by mixing the incoming signal with the VFO or synthesizer. This
known constant frequency is the I F. Next the IF is converted into audio via a
discriminator (in the case of FM). I F Bandwidth; Intermediate Frequency
bandwidth. The width of the band of signals that can pass easily through the
intermediate frequency stage of a superheterodyne receiver.
INFRARED
That
portion of the electromagnetic spectrum located at frequencies just below
visible light; in fact, the lasers used for so-called " long-wavelength
" fiber optics communications at 1300 nanometers are really in the "
near-infrared " region, producing an extremely deep ruby red color of such
purity and strength as to damage human eye retina.
INITIALIZE
Setting
all counters, switches, addresses or pointer registers to zero or the beginning
of, or at prescribed points in the operation of a computer routine. As related
to the "reset" of a Packet node or "rebooting" a computer.
INPUT/OUTPUT
(I/O) CHANNEL/PORT
In
computers, the hardware function, usually a bus of parallel wires, hence
"channel," that transports data in parallel form between the CPU and
peripherals like storage, printers or communications.
INTELLIGENT
TERMINAL
A
terminal containing a programmable processor capable of some degree of local
processing; the range of functions and degree of capability is not standardized
and subject to wide discussion of what constitutes "intelligence."
INTERACTIVE
Involving
a duplex, "conversational" exchange between a user and a computer.
INTERFACE
The
junction or point of interconnection between two systems or equipment having
different characteristics; has both hardware and software implications. Most
interface references related to Packet Radio refer to the cabling between the
TNC and transceiver, or between the computer and the TNC.
INTERFERENCE
Any
unwanted noise, crosstalk or spurious signals on a communications circuit that
acts to reduce the intelligibility of the desired information signal or speech.
INTERLEAVING
(INTERLEAVE)
In
Packet or data communications, interleaving may be a character or bit
interleaved, with optimum applications for each. A technique to minimize effects
of error bursts on message throughput by interleaving groups of characters or
blocks that approximate the burst length.
INTERNATIONAL
STANDARDS ORGANIZATION (ISO)
A
world standards body that generally sets standards for any product fabricated or
manufactured. ISO is resident in Geneva, Switzerland.
INTERNET
The
Internet is a public system of computers which communicate over commercial lines
(usually telephone or fiber optic leased telephone lines) using TCP/IP. Usage of
the Internet network is free. Usage of the computers that are connected through
other services to the Internet are not free. Most people who have access to the
Internet either pay a fee or having a connection to the network from work or
school.
IP
- Internet Protocol.
The
core protocol of the ARPA suite IP is a simple protocol that handles addressing,
fragmentation and type-of-service routing in the heterogeneous internet
environment
IS
- Intermediate System.
ISO's
term for a packet switch.
ISO
standards apply to physical aspects of the "25-pin connector" of CCITT
V.24/28 data interfaces (RS-232), definitions of several layers of data networks
for which different hardware units may be required, and such diverse things as
the exposure speeds of photographic film and definitions of units of
measurement.
INTERRUPT
Data
processing term for a processing stoppage made in such a way as to be resumable.
Compare to a " halt ," typically meaning a stoppage that requires
initializing the machine to restart processing.
ISDN
(INTEGRATED SERVICES DIGITAL NETWORK)
A
global plan under auspices of the CCITT to provide any information service users
may desire on a single worldwide public switched network. The ultimate ISDN has
as its goal the elimination of need for discrete telephone, telegraph, data,
packet and other networks as well as physically dedicated " special
services " circuits as now required to provide broadcast, video, high-speed
data and numerous functions users want
J
JHEARD
A
command associated with the PBBS and mailbox features of many popular TNCs. When
the Jheard command is invoked, a list of the most recent or "just
heard" stations will be displayed. If the Jheard command is executed with a
"JL", the paths indicating the stations callsign, origin, and
digipeaters will be displayed.
JITTER
Short
term instability of the amplitude and/or phase of a signal. The latter condition
is commonly called PHASE JITTER. Variations in the phase or amplitude of a data
modulated signal having no relationship to the data. In amateur packet signals,
phase jitter may cause error in decoding the data.
JNOS
A
version of KA9Q NOS written by WG7J that combine a BBS, node, and conference
server.
JUMP
SCROLLING
Characteristic
of a terminal with vertical motions of a whole line of characters at a time in
discrete steps of one line, much as a teleprinter terminal might do. Contrast
with " smooth scrolling " as done by graphics terminals.
K
KANTRONICS
Kantronics
designs, manufactures and markets a range of amateur packet products including
the popular KPC TNCs and KAM multimode controller.
Ka
BAND
Microwave
radio frequencies in the region of 20 to 30 gigahertz, portions of which are
used for local microwave " bypass ," notably the region near 23
gigahertz , while future satellite applications have allocations reserved as
well.
Ku
BAND
Microwave
radio frequencies in the region of 10 to 20 gigahertz, portions of which are
used for satellite (notably VSAT) operations at 12 to 14 gigahertz and local
terrestrial " bypass " at 10 and 18 gigahertz.
KEYBOARD-TO-KEYBOARD
Communications
between two packet user stations in real time. A fun part of Packet radio that
is again being experienced by many Packet users. Emergency digital
communications are but a few ways that keyboard-to-keyboard is useful.
KISS
Keep
It Simple & Short. The TNC operating mode where the TNC merely translates
packets between half duplex, synchronous HDLC on the radio port and full duplex
asynchronous SLIP framing on the host port; the host computer must implement all
higher level protocols, including AX25 if it is used. . The KISS TNC is only
responsible for TX delay and DCD hold-off. Kiss is used with TCP/IP hosts and
also often used with BPQ and other such PC based packet switches.
L
LAN
- Local Area Network:
A
LAN is the user access point, be it node, gateway or cluster. LAN users which
are home stations running minimum antenna and power configurations to access the
node may access multiple servers through the network via the local access node
LASER
Acronym
for: Light Amplification by Stimulated Emission of Radiation; converters of
electrical energy into light of great purity and thus controllability adequate
for telecommunications by guiding the energy along glass waveguides; used more
commonly for high-capacity, long-haul fiberoptic links of common carriers; the
fiber links of end users most commonly employ less expensive Light Emitting
Diodes ( LED ) for shorter distances and lower capacities.
LATENCY
Used
by some to describe the time delay from the point when a Packet network station
seeks access to a channel and the time access is granted by the network; an
evolving term unique to certain LANs.
LAYER;
LAYERING; LAYERED ARCHITECTURE
Nomenclature
of the OSI Reference Model for data transport that defines the functions in each
step of a hierarchy of operations that must occur in order to transfer
information between points.
LED
(LIGHT EMITTING DIODE)
A
semiconductor device that emits light under proper electrical conditions. Used
both for simple indicators on electronic equipment and (with proper selection
and use)as the source of signals for short-range (multimode) fiber optic
transmission systems.
LEVEL
An
expression of the relative signal strength at a point in a communications
circuit compared to a standard; the standard is most often 1 milliwatt of power
at a frequency of 1000 Hertz in a 600 Ohm load. The output impedance of most
terminal node controllers is 600 ohms.
LINE
PRINTER
Descriptive
of computer printers that set and print an entire line of data at a time.
--e.g., Line-printer or LPT1; Often indicative of a high-speed, high volume
printer. LINE SIDE - Descriptive of observing from or sending into the
transmission path.
LINK
LAYER
The
logical second layer of the OSI Reference Model for Open Systems
Interconnection, located between the Physical and Network layers. Level 2 in the
7 layer OSI computer communications protocol set. AX.25 is the amateur packet
level 2 protocol.
LOCAL
AREA NETWORK (LAN)
When
associated with amateur radio Packet, the term defines an area or locale where a
group of Packeteers use the same frequency to converse, or receive messages into
their personal Packet mailbox (SEE ALSO "LAN").
LOOPBACK
A
test in which the output of a modem modulator or other full-duplex digital
device is looped back to the input of the demodulator or device. The looped back
signal may be either analog or digital. LOOP BACK (pinging) - A transmission
testing method of simply having the distant node (end) on a network send back
the signals it receives for evaluation at the transmitting end.
LOCKED
NODE
TheNET
nodes have the capacity to generate routing lists automatically based on
parameters set in the node's RAM. The parameters specify default quality values
to be assigned to routes to each neighbor, separately defined for radio port
neighbors and RS-232 port neighbors.
LOCKED
ROUTE
TheNET
nodes have the capacity to generate routing lists automatically based on
parameters set in the node's RAM. The parameters specify default quality values
to be assigned to routes to each neighbor, separately defined for radio port
neighbors and RS-232 port neighbors. It is possible using the sysop's ROUTE
command to manually set a route at a specified quality. e.g. [Route Port CALL/SSID
+ VALUE]
EXAMPLE:
[R 0 K4ABT-7 + 192]
LOS
(LINE OF SIGHT)
Descriptive
of the use of free-space communications technologies requiring an unobstructed
path between transmitter and receiver, as in microwave radio, satellite
communications, and infrared optical communications links.
MAIL
BOX
A
personal BBS in a TNC. Sometimes also refers to any personal BBS system handling
personal mail. (Also called; Mail Drop, PMS, Personal BBS, PBBS )
MAIL
DROP
A
part of a TNC program that allows messages to be loaded into the TNC and then
retrieved from over the air or from the terminal at the TNC
MARK
One
of two possible binary states in data communications. The mark is the resting
state in an asynchronous serial system. The negative voltage state on a RS-232
port is called mark. One of the two tone in an AFSK modulation is mark. (See
"space" the opposite state). MARK - The signal state on a binary
channel representing a "1." Corresponds to current on, hole in paper
tape, and (usually) negative voltage, as in EIA RS-232.
MAPPING
In
network operations, the logical association of one set of values, such as
addresses on one network, with quantities or values of another set, such as
devices on a second network; this might be name-address mapping, and
internetwork-route mapping. MATRIX - SEE "DIODE MATRIX"
MEGAHERTZ
(MHZ)
a
unit of a million Hertz; meaning millions of cycles per second of AC current.
MESSAGE
In
Packet Radio or telecommunications in general, a complete transmission of data
or information. Usually associated with "block" in data
communications, as 256 characters.
MFJ
- MFJ Enterprises Inc.
MFJ
designs, manufactures and markets a wide range of amateur Packet products such
as the popular MFJ-1270C TNC (TAPR TNC-2 clone) used for network construction
when installing theNET X-1J4 and other network protocol EPROM.
MICROWAVE
(M/W)
Radio
transmission using very short wave-lengths, corresponding to a frequency of
1,000 megahertz or greater, and not subject to "back-hoe fades."
MIR
Russian
(Soviet) space station whose cosmonauts regularly use packet radio to
communicate with amateurs around the world.
MODE
This
section concerns the X1J4, 17 MODE feature-commands. "See also X1J4 MODE
& PARAMETER WEB PAGES" .
MODEM
Contraction
of the term Modulator/Demodulator; device that modulates and demodulates signals
on and off. Each TNC supports a data modem.
MODEM
HEADER
The
connector inside a TNC used to connect an external modem to the TNC for higher
speed or a different mode of communication. All the data and control lines from
the CPU to the modem pass through this connector.
MODULATION
Alterations
in the characteristics of analog carrier waves, impressed on the amplitude,
phase and/or the frequency of the wave.
MSYS
An
amateur packet BBS software written by WA8BXN. Latest Versions also contain
DxCluster and conference modes. MSYS has support for TheNET routing and emulates
a TheNET node. Note that MSYS's simulation of TheNET is limited by the
performance of the PC and may be very poor when the PC is doing BBS operations.
The MSYS TheNET emulation features are best utilized as a way to pipe user
traffic in and out of the board via the TheNET style node mnemonic.
MTBF
(MEAN TIME BETWEEN FAILURE)
A
statistical method developed and administered by the U.S. military for purposes
of estimating maintenance levels required by various devices and systems.
MULTIPLE
ACCESS
In
Packet Radio communications, the capability to function as part of the
communications link between more than a single station. When accomplished with
analog methods, FDMA is the term; if digital, TDMA.
MULTIPLEX/MULTIPLEXING
Transmitting
more than a single message simultaneously on a physical transmission path; if
analog, the technique is FDM, but if digital it is TDM.
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N
NACK/NAK
"Negative
Acknowledge" character in many data codes; typically used to indicate
receipt of a corrupted message, ordering retransmission; compare to "REJect"
character in Packet Radio nodes. Negative AcKnowledgement. A packet or AMTOR ACK
response that indicates that the data was NOT received correctly.
NEIGHBOR
In
a network of nodes the neighbor of a node is any node that is talked to
directly, via the RS-232 port, or via the radio port.
NET/ROM
A
proprietary product of Software 2000, that Implements AX-25 at the link layer
(L2), with adhoc protocols at the network (L3) and transport layers. Also
provides incoming or outgoing regular AX.25 level 2 connections to internal
transport layer connections. Provides automatic routing between NET/ROM nodes
but the user is still responsible for "source routing" between the end
NET/ROM nodes and the ultimate source and destination.
NETWORK
A
collection of terminals, computers, peripheral devices, and Packet Radio nodes
connected to one another for a defined purpose of Packet Radio networking. A
network is a system of nodes interconnected in such a way that any node can
communicate with any other node in the system in an efficient and speedy manner.
An example would be a network of user ports wire-linked to backbone nodes that
are in turn connected to each other by UHF point-to-point links.
NETWORK
INTERFACE
The
point of interconnection between one Packet Radio network and another. In most
applications it is called a "Gateway."
NETWORK
LAYER
Generically,
any of several functions in a Packet Radio communications network, such as
Terminal, Switching and Transmission. Specifically in the OSI Reference Model,
the third layer, servicing the Transport Layer, ensuring that information is
properly routed throughout the network. Level 3 of the seven layer OSI
communications protocol set. The network layer specifies the communication
between adjacent nodes or networks and interfaces with the user at the level 2
link layer and with distant nodes at the level 4 transport layer protocol.
NETWORK
TOPOLOGY
Descriptive
of the physical and logical relations of nodes in a network; the schematic
arrangement of the links and nodes; often classed as star, ring, tree or bus
topology; detail variations and hybrid combinations abound.
NETWORK
TRUNKS
Long
path dedicated links or nodes which interconnect other backbones and LANs.
NETWORK
VIRTUAL TERMINAL
A
Packet Radio communications concept in which a variety of DTE's with different
data rates, codes, speeds, formats and protocols are accommodated on a single
network. In such networks, Network Processors convert all into a common format
for exchange between processors, then reconvert as needed to output data
elsewhere.
NODE/NETWORK
NODE
A
termination point for Packet Radio communications links; in the sense of Packet
Radio communications, a node equipped with an X-1J4 EPROM. An active element in
a network, this means any connect, from a user station to a bulletin board. A
node in Packet radio is an intelligent router of real time data, somewhat more
intelligent than a digipeater but faster than a store and forward BBS. (See
TheNET).
NODE
BROADCASTS
Each
node transmits a message out at quarter or halfhour intervals, depending on the
settings the SNO has installed. This message tells the neighbor nodes what nodes
are contained in the nodes table. The neighbor TheNET nodes interpret this
information based on the "quality" setting in the node parameters.
NODE
KNOCKING
or
Node hopping is denoted as a user who constantly DXes the network by the process
of connecting from one node to the next along a path and checking the routes
available by reading the nodes table, nodes list and INFO response. One of the
features of TheNET X-1J4 is that a user may hunt through a network and take
advantage of local Routes commands to determine what all ofthe neighbors ofa
particular node are. With this knowledge the user may then connect to a neighbor
node and repeat the process.
NODE
STACK
Two
or more nodes on one site interconnected by a diode matrix.
NOISE
Unplanned
energy introduced into a communications channel, resulting in transmission
errors.
NOS
- Network Operating System.
NOS
is a program which is generally used to communicate using the TCP/IP protocols
but may actually be much more than just a program that does TCP/IP. NOS runs on
a personal computer and is the name used to describe many different programs
that perform in a similar manner.
NOVRAM
Non-Volatile
Random Access Memory, is a memory chip which contains its own power source and
holds the present memory, even if the power is removed from surrounding
circuitry. External commands provide a means to change the memory. A storage
medium that does not lose its contents when power is removed.
NRZ
Non
Return to Zero. A binary code format in which binary ones and zeros are
represented by two discrete voltage levels and the voltage remains at the
indicated level for the duration of the code bit. Compare with bipolar pulse
modulation in which the signal would return to an average level between bits.
NRZ is the form that most binary signals take within computer circuitry.
NRZI
Non
Return to Zero Inverted. A binary code format in which a data 0 (zero) produces
a transition (either from 0 to 1 or from 1 to 0) in the code. It does not mean
that the NRZI code is merely inverted. The main advantage of NRZI is that it
does not matter at what point in the transmission that one starts to decode, the
subsequent data will be the same. The code signal actually sent to the modem and
transmitted by an amateur packet TNC, is in NRZI format. At the receive end the
TNC converts it back to NRZ format for the CPU to process.
NULL
MODEM
A
interconnect device or data cable used to connect together two DCE or two DTE
digital devices. The RS-232 TXData/RXData and RTS/CTS lines are swapped.
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O
OBSOLESCENCE
COUNT
In
a NET/ROM or TheNET system, each node entry in the nodes table is given an
"initial obsolescence count" each time the route is confirmed by a
neighbor's node broadcast. The obsolescence count is reduced at regular
intervals. When the obsolescence count reaches a predetermined value, the node
entry is considered obsolete and is no longer broadcast to its neighbors.
OSI
Open
Systems interconnect. The OSI is a project of the International Standards
Organization to develop a set of computer communication protocols. The OSI is a
framework with which communications protocols are described.
OVERHEAD
That
part of a Packet frame that contains the address, routing, and error-correcting
components that support the message delivery to the target station or node. Some
node protocols have less overhead than others.
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P
PacComm
Packet
Radio Systems Inc. PacComm designs, manufactures and markets a range of packet
radio products, both amateur and commercial.
PACKET
Amateur
AX.25 communications, a structured group of binary digits in a prearranged
sequence containing synchronization, address, control an error-checking data. A
packet is a block of many characters (or bytes) which are sent together along
with a few extra characters (overhear/checksum) used to guarantee that the data
is completely error free. The packet includes addressing information so that the
receiving station knows the source and destination of the Packet.
PacketCluster
A
proprietary software from Pavilion Software. It creates a specialized system for
DXers and operates with all users connected in such a way that DX information
can be distributed in "real time".
PACKET
NETWORK
A
network dedicated to the routing and delivery of data through-put in the form of
standardized "packets." Example is the SouthEastern Digital
Association Networks (SEDAN), an AX.25/X1/X2 network
PACKET
SWITCHING
The
technique in which a stream of data is broken into standardized units called
"packets," each of which contains address, sequence, control, size and
error checking information in addition to the user data.
PAD
Contraction
of the term Packet Assembler/Disassembler in Packet Switched networks, the
instrument that converts data between steady streams and packets. A device that
interfaces our computer or "dumb" terminal to an X.25 packet network.
It gathers typed characters into outgoing packets and translates incoming
packets back into serial asynchronous data streams. Also provides a simple
command interpreter for setting up and tearing down connections, controlling
parameters, etc. The amateur packet radio TNC was called a "PAD" in
the early days of Packet Radio.
PACSAT
An
amateur radio satellite carrying a packet store-and-forward node. When launched
became OSCAR 16.
PACTOR
PACket
Teleprinting On Radio. An HF digital communications protocol developed in
Germany. PACTOR combines the best features of both AMTOR and Packet for
improved, and more efficient HF data communications.
PARALLEL
TRANSMISSION
Simultaneous
transmission of all parts of a signal at one time; in data transmission,
requiring a separate signal path for each of the bits of a character; internal
to computers, this is called a "parallel bus."
PARAMETERS
In
TheNET X-1J4 nodeware there is a list of values used by the System Node Operator
(SNO) to configure options within the node. These 26 values affect 85 percent of
the X-1J4 node personality. The balance of the X-1J4 behavior is controlled by
the 17 "MODE" commands. (See also MODE) "See also X1J4 MODE &
PARAMETER WEB PAGES"
PARITY
a
constant state of equality; one of the oldest and simplest methods of error
checking data transmission. Characters are forced into parity (total number of
marking bits odd or even as selected by choice) by adding a one or zero bit as
appropriate when transmitted; parity is then checked as odd or even at the
receiver. For odd parity, a 1 or 0 bit is added to 7 data bits so that the total
bit count is an odd number. For even parity, the total bit count is made even
with the parity bit. Parity words can similarly used with groups of binary
words.
PARITY
BIT
a
check bit appended to an array of binary digits to make the sum of all the
digits always odd or always even.
PARITY
CHECK
a
checking method that determines if the sum of all the digits in an array is odd
or even.
PATH
This
word is used to mean the nodes, digis and servers that must be used to pass data
from one point to another. Often a path may be specified without including some
intermediate nodes if the knowledge of those nodes is not necessary to pass the
data or make a connection.
PBBS
Personal
Bulletin Board System (see also PMS). Either Personal Bulletin Board System or
Packet Bulletin Board System. The former is called personal mail drop or
personal mail system (PMS) to avoid confusion. PMS indicate a mail box that is
contained inside a normal user TNC, as in "personal message system." A
limited function BBS contained within a users TNC firmware with which the user
can enter or receive personal messages from other users or from the nearest full
service BBS. Usually referred to by one of the commercial trade names such as
MailBox, PBBS, PMS, Mail Drop, etc.
PC
- Personal Computer.
Usually
refers to a computer that is identical in function to a product by IBM that was
marketed as an IBM PC. They are more correctly referred to as IBM compatible PC.
PC could mean any kind of computer that is used by an individual for general
purposes (i.e. Ilot a microwave oven control panel). It is sometimes hard to
determine if a person who mentions PC is referring to a generic personal
computer or specifically an IBM PC compatible.
PHYSICAL
LAYER
Layer
1 within the OSI Reference Model for Open Systems Interconnection; providing
electrical, mechanical and handshaking procedures for transmission.
Example:
RS-232 is a Layer One function.
PID
Protocol
ID. The first byte of the packet frame which identifies which protocol is used
for the packet frame.
PLL
Phase-Locked
Loop. A circuit using feedback methods to control the frequency of an
oscillator. Usually used as frequency control in synthesized radios.
PM
Phase
Modulation. A modulation technique in which the phase of the carrier is changed
in relation to the modulating signal.
PMS
"Personal
Message System" (See also PBBS)
POINT-TO-POINT
A
Packet Radio communications circuit between two terminals only. No intervening
node.
POLLING
In
packet terms, polling is a collision avoidance method in which one master
station queries each of the users on the channel if they have a packet to
transmit. The slave stations will not transmit until they have been
"polled" by the master station. In this way no two stations will
transmit at the same time thus avoiding collisions.
PORT
Entrance
or access point to a computer, multiplexor device or Packet Radio network where
signals may be supplied, extracted or observed. An input/output channel or
connector on a node or TNC. A TNC normally has one or more radio ports hooked to
a radio transceiver(s) and a RS-232 or serial port that may be connected to the
users terminal (computer) or another node serial port in the case of a TheNET
(or other type of higher level node) node stack. A port may also refer to a
special purpose node such as a user-port, IP port, backbone port, etc.
PRESENTATION
LAYER
The
Presentation Layer is where Packet Radio messages that are to be transmitted are
grouped, formed, converted to and undergo conversion between computer and the
terminal node controller.
PROCESSING
DELAY
In
Packet Radio communications, the time taken by a computer to operate on an
inbound message and return a response; frequently not accounted for in
complaints of telecommunications response time problems.
PROM
Programmable
Read Only Memory. (See EPROM)
PROPAGATION
DELAY/PROPAGATION TIME
The
time period between injecting a signal into a communications frequency and its
exit at the target end. While not significant to speech, propagation delay can
be restrictive to data and Packet.
PROTOCOL
A
communications protocol is the set of rules and procedures used to implement a
technique or method of communications. The rules for maintaining communications
between similar devices. As with AX.25 maintaining orderly error-free data flow
and data link control. A set of procedures for establishing and controlling the
transmission of information. There are many different protocols for many
different purposes. AX.25 is a protocol which describes how small computers can
talk to each other. e.g., SDLC; Bisync.
PROTOCOL
CONVERSION/PROTOCOL CONVERTER
Generic
name and name of the devices that perform a widely variable set of conversions
of code, speed, electrical interface and/or block formatting and error
checking/correction in data circuits.
Example:
a packet network TNC operating between an ASCII terminal and a packet network is
a form of protocol converter. When the function is to make the line signals of a
particular terminal appear like another, the protocol converter is a type called
a Terminal Emulator.
PSK
- Phase Shift Keying
A
data modulation method in which binary data is encoded as discrete changes in
the phase of the carrier signal. In amateur packet, PSK is used mainly on OSCAR
satellite data communications.
PULSE
In
communications, typically a signal characterized by a constant amplitude and
duration; the line signal representation of a binary digit.
PULSE
CODE MODULATION (PCM)
The
form of digital transmission in which information for transmission is sampled at
regular intervals and a series of pulses in coded form are transmitted
representing the amplitude of the information signal at that time. The most
common form of PCM in North America is one in which analog signals of less than
4 kilohertz are sampled 8,000 times per second and converted into an 8-bit code,
resulting in 64 kilobits per second for transmission. Twenty-four of these
streams are Time Division Multiplexed into a 1.544 megabit stream for T-1
transmission. The European equivalent is 30 channels in a 2.048 megabit stream.
PULSE-LINK
REPEATER
Connects
two E&M signaling circuits back to back, changing the E of one circuit to
the M of the other and vice versa.
PULSE
MODULATION
The
modulation of a series of pulses to represent information-bearing signals.
Typical methods involve modifying the amplitude (PAM), width (PWM), duration (PDM)
or position (PPM). Pulse Code Modulation (PCM) is the most common modulation
technique involved in telephone work.
Top
--------------------------------------------------------------------------------
Q
QRM
Man-made
interference on a radio frequency, intentional or not. QRN Natural interference
on a radio frequency. Lightning, solar noise (very week signal work) are
examples of natural interference.
QPSK
Quadrature
Phase-Shift keying.
QUEUE
A
delay in forwarding data or traffic caused by the inability of the system or
network to handle the quantity of data being attempted.
Top
--------------------------------------------------------------------------------
R
RADIO
FREQUENCY
A
broad part of the electromagnetic spectrum ranging from above audio frequencies
to beneath infrared; characterized by the use of antennas to couple signals to
the Earth's magnetic field.
RAM
Random
Access Memory; That part of a computer or TNC that is holding data, or memory
during the power "ON" period. If the RAM has "battery
backup" the memory is remains in the RAM until it is changed. If the RAM
has no battery backup, no memory remains when power is removed. An IC in a
computer that holds data only so long as power is applied. The RAM is usually
used only for storage during the execution of a program. TNCs use RAM for
temporary storage of messages and parameters. Normally TNC RAM is powered
(batttery - backed) all the time using a lithium battery in the TNC.
RASTER/RASTER
SCANNING
Providing
a means to place information on a screen by sweeping it completely from side to
side an top to bottom in a regular fashion. Both CRT tube displays and fax
machines utilize forms of raster scanning.
REALTIME
Processes
that occur instantly as they occur; closely related to "online. When a
signal is sent and a result is expected back with a short enough time to fall
within a person's attention span the operation is said to be in Real Time.
Keyboard to keyboard operation is real time. Keyboard to server is realtime.
Sending a message to a friend via a pack BBS is not real time because the sender
doesn't know how long it will be before the reveiver answers back.
RECORD
In
data processing, one complete group of logically related information; closely
related to "block" and "packet" in communications
technology.
RESIDUAL
ERROR RATE/UNDETECTED ERROR RATE/LATENT ERROR RATE
The
error rate at higher levels of Packet Radio communications system resulting from
inability of the error detection/correction methods to trap all errors.
RESPONSE
TIME
A
measure of time from entering a data field on a remote terminal until the
response is delivered to the remote by a central computer; a frequent measure of
the overall performance of a Packet Radio Node Network (PRNN). The time between
sending data to a remote device before an expected response returns to the
originating station. RETRY - Retry is the process by which a packet that is sent
and not acknowledged will be resent by the sending station. This retry is
repeated until the acknowledgment is received or until a "retry
counter" reaches its limit and the circuit is terminated.
ROM
Read
Only Memory. A non-volatile memory IC used to permanently store operating
programs in computers and other digital devices. ROMs come in many forms such as
FROM (field Programmable ROM), EPROM (Erasable Programmable ROM), EEPROM
(Electrically Erasable Programmable ROM), OTP (One Time Programmable ROM), etc.
ROM
IMAGE
The
set of binary data that is programmed into an EPROM.
ROUTE
DIVERSITY
Two
(or more) Packet channels that assume two physically separate routes. A TheNET
type node will substitutes an alternate path if the main path is lost thus
preventing total loss of service.
ROUTING
The
process of determining or prescribing the path a connection will take through a
network of nodes.
ROUTING
TABLE
A
matrix associated with a Packet Radio network control protocol giving the
preferred network link directions beyond that point. (See locked-routes for
Packet nodes).
RS-232
A
set of signals accepted as a "standard" by the Electronics Industries
Association (EIA), designed to make the interfacing of computers and networks,
easier. RS-232-C is the current Electronics Industry Association (EIA) standard
for the most common signals used between computers. A signal which uses the
RS-232 standard is often said to be RS-232. The computer to TNC connection uses
RS-232 signals. Normal computer internal data signals use ground and +5 volts to
indicate a zero or a one.
RTS
- Ready To Send
A
control on a RS-232 port that indicated that the device has data ready to send.
On some devices the DTR line is used instead of RTS. RTS is often used in
conjunction with the CTS signal to engage "hardware handshaking."
RTTY
- Radio TeleTYpewriting
An
early mechanical based method of data communication on radio using the baudot
code. In 1980 ASCII was also permitted on RTTY in the US. TELEX and TWX are
commercial telephone systems using the same techniques.
RUDAK
Regenerativer
Umsetzer fur Digitale Amateurfunk Kommunikation; Meaning, Regenerating
Transponder for Digital Amateur Communications. A packet transponder project
flown on board OSCAR 13 satellite. Developed by AMSAT-DL group in Germany.
RXData
Received
Data stream produced by a modem demodulator.
S
SAREX
Shuttle
Amateur Radio EXperiment. An educational program in which U.S. Shuttle
astronauts communicate with classroom students using voice and packet.
SATURATION
(Sometimes
called "GridLock") When related to Packet Radio, this definition
refers to the absolute limit of traffic handling that a network of nodes will
accept or handle.
SCATTERING
Diffusion
of an electromagnetic signal as it passes through a transmission medium; the
ultimate cause of signal loss with distance in fiberoptic lightpipes.
SERIAL
PORT
The
part of a computer responsible for sending binary data in a serial fashion.
Normally computers talk intenally with parallel data signals, that is that all
of the important bits for a block ofinformation are sent at once. Serial
communications uses only one wire which is toggled many times for a single block
of information. Thus a letter A might be sent in parallel all at once when it
must be sent as a string of ones and zeros in sequence in serial. The serial
port usually consists of a single chip called a UART, a RS-232 driver chip and a
connector.
SERIAL
TRANSMISSION
transmitting
data characters or bytes one bit at a time, in sequence. Contrast with: Parallel
Transmission.
SERVER
In
telecommunications traffic engineering, the generic term for a register or
outgoing line that would provide the connection a subscriber demands. In LANs, a
processor providing specific services to network users, as a file server to
manage orders for file access, a gateway server to manage exit and entry of
information to LAN users and similar LAN operations. This may include BBSs,
DxClusters, DOSgates, TheNET nodes, TCP/IP hosts etc.
SESSION
Engaging
two terminal nodes of a network in a logical connection for information transfer
SHANNON'S
LAW
a
statement defining the theoretical maximum at which error-free digits can be
transmitted over a bandwidth-limited channel in the presence of noise. The rough
equation works out to about 10 bits per hertz of bandwidth in practical analog
circuits.
SIDEBAND
The
resultant added signals above and below a carrier frequency resulting from the
modulation process placing information on the carrier. Telephony has in most
systems for years filtered out one of the sidebands to save transmission space
in AM analog systems. The resulting sideband is called "single
sideband." In recent years this same technique has been applied to FM
microwave radio as well, resulting in twice the transmission capacity.
SIGNAL
Energy
intentionally introduced into a transmission path for the purpose of
transmitting information.
SIGNAL
TO NOISE RATIO
Ratio
of the signal power to the noise power in a specified bandwidth, usually
expressed in decibels; the smaller the ratio, the poorer the channel. Generally
speaking, a ratio of 20 db or more is a channel subjectively
"excellent" for voice, while broadcast television video requires 30 db
or more, but 1200 bps can function with only 12 db, requiring greater S/N as the
baudrate increases.
SIMPLEX
A
channel capable of transmitting in one direction only.
SINGLE
SIDEBAND RADIO (SSB)
A
form of amplitude modulation of a radio signal in which only one of the two
sidebands is transmitted. Either of the two sidebands may be transmitted while
the carrier may be reduced or suppressed (see SIDEBAND above).
SMART
TERMINAL
A
Packet Radio terminal or computer capable of operating in either a
conversational or a block mode; containing a full set of local editing
capabilities without reliance on a controlling external computer.
SPACE
The
communications signal state corresponding to binary zero; represented as no
current, no hole in paper tape, (usually) positive voltage. See also
"Mark."
SPREAD
SPECTRUM
Fundamental
to telecommunications, a method of transmitting radio signals as a very wideband
but low-powered signal that appears almost like noise. At the receiver all
components of the desired signal are filtered from the noise and summed to
recover a usable signal
SSID
The
SSID is the specific number applied the call sign of a digipeater or second,
third, etc...packet stations. The acronym is derived from the term,
"Secondary Station IDentification." It is most often used with nodes
of the TheNET variety. Secondary Station IDentification. In Packet radio, a
callsign is normally used as an address. In a applications where an amateur
requires more than one address on the air at a time the callsign may be used
with an "ssid." There are 16 different possible SSIDs, 0 through 15.
An SSID is used when applied to a personal mailbox or PBBS by adding the dash
one suffix to the call. Most personal mailbox calls use -1 as the SSID. i.e. the
Packet mailbox of K4ABT is K4ABT-1.
Below
is an example of a few nodes and callsigns of K4ABT and associated SSIDs located
in central Virginia.
·
K4ABT User call of my home Packet station.
·
K4ABT-1 Mailbox call/SSID at home QTH
·
K4ABT-2 (223.700 Mhz.) 9600 baud node at Big Island Mtn, VA
·
K4ABT-3 (223.700 MHz )( 145.770 MHz) Gateway/Port SML mountain, VA.
·
K4ABT-6 (145.770 MHz )( 223.700 MHz) Gateway/Port SML mountain, VA.
·
K4ABT-7 (145.770 MHz) 1200 baud node at Big Island Mtn, VA
·
K4ABT-9 (440 MHz.) 9600 baud backbone node.
SIMPLEX
A
communication method in which communication between two stations takes place one
direction at a time regardless of whether the receiving and transmitting on the
same frequency or on split frequency. Amateur radio, simplex usually means
receiving and transmitting on the same frequency. Most Packet communications are
conducted in "simplex."
SIMPLEX
DIGIPEATER
A
digital store-and-forward node or digipeater is a regenerative digital repeater
that receives a packet, verifies that it was received correctly, and if the
Packet is correct, retransmits it on the same frequency it was received on. The
node retransmits the signal only after confirming that the frequency or channel
is clear.
SITE
MANAGER
This
is the person or persons who are responsible for node performance relating to
hardware maintenance.
SITOR
A
commercial communications system very similar to AMTOR and used mainly for
maritime and marine mobile communications.
SLIME
TRAIL
In
Net/ROM and TheNET nodes, transmitted node tables will sometimes show distant
nodes that connect through it. The temporary node will be listed at the
beginning of the nodes list and will show callsigns only, no alias. This node
list entry is called a "slime trail" because you can trace back to see
the origin and route of the displayed node.
SLOTTIME
In
the persistence method of collision avoidance, slottime is the time delay before
repeating the random number persistence calculation. (See persistence)
SPACE
-
Space, like mark, is one of the two possible states in a binary communications
system. In asynchronous serial systems, the start bit is space. On a RS-232
port, the positive voltage level is space.
STA
Special
Temporary Authorization. A special permit granted by the FCC to operate using a
special application for experimental or test purposes. STA's are also issued to
stations for use in applications that are not normally permitted or allowed.
START
BIT
The
leading bit of every asynchronous character, needed to trigger the receiver that
a new character is starting; must intrinsically be a space (0) bit.
STATION
Any
user location on a Packet Radio network capable of sending or receiving Packet
AX.25 transmissions.
STORE-AND-FORWARD
This
is the process employed in nodes and digipeaters where a packet is received,
processed, and retransmitted to the next node, digipeater, or destination
station.
STREAM
AX25
allows many connections to be made from several stations at the same time. Each
connection is called a "stream." To test one's sanity, open more than
one stream and allow two or more connections, then carry on separate QSO's with
each separately connected station.
SWITCH
Mechanical,
electromechanical or electronic devices for making, breaking or changing
connections in circuits.
SYNCHRONOUS
A
serial communications mode in which the data bits are sent in a continuous
stream without character start and stop bits. The data stream is embedded with
clocking bits for synchronization at the receive end of the circuit. AX.25
packet communications use synchronous data transmissions.
System
Node Operator (SNO)
The
person(s) responsible for the contigious operation of a network node. Duties
include checking for legal operations. SNO's are not sysop's (See System Node
Operator.
SYSOP
- or BBS SYSOP
The
person(s) responsible for the smooth operation of a BBS, including maintaining
forwarding routes, redirecting misaddressed messages, checking for illegal or
improper messages. SNO's are not sysop's (See System Node Operator.
SYNCHRONIZATION
Relating
to Packet Radio, the function of terminal node controllers to reach equal
clocking of data and recognized frames.
SYNCHRONOUS
Having
a regular time relationship between successive bits, characters, blocks, frames,
messages or other elements. Even so-called "asynchronous" data reaches
synchronization during the reception of information bits for each character.
SYSTEM
NODE OPERATOR (SNO)
This
is the person or persons who have software and hardware control responsibility
for node (and digipeater) operations over specific node site(s).
T
TAPR
Tucson
Amateur Packet Radio Corp: " non-profit" research group best known for
the TNC1 & TNC2 TNCs and their clones. Tucson Amateur Packet Radio, PO Box
12925, Tucson AZ 85732-2925.
TCP
Transmission
Control Protocol. A major element of the ARPA suite. TCP Provides the connection
oriented byte stream on an end-to-end basis. TCP runs atop IP and is maintained
at the transport and session layers.
TCP/IP
Transmission
Control Protocol / Internet Protocol. The KISS mode activates this mode in some
TNCs. This mode is not supported by software for all computers and Terminal Node
Controllers (TNCs). The KISS protocol was used by Phil Karn KA9Q, to develop the
Packet radio version of TCP/IP.
TELECOMMUNICATIONS
The
transmission of voice and/or data through a medium by means of electrical
impulses and includes all aspects of transmitting Packet Radio information.
TELEGRAPH
A
system employing the interruption of, or change in, the polarity of signaling to
convey coded information. Many of todays techniques in data communications
follow precepts first established in telegraphy.
TELEMETRY
Discipline
of measuring a quantity or quantities, transmitting the results to a distant
point and there interpreting, indicating or recording the quantities measured.
TELENET
A
presentation protocol layer in the ARPA & TCP/IP suite used for keyboard to
keyboard and keyboard to host communications.
TERMINAL
Relating
to Packet Radio, a device capable of sending or receiving information over a
Packet Radio frequency. A terminal or display input/output (I/O) device. A
Cathode Ray Tube (CRT) normally referred to as a terminal. They are often
referred to as "dumb terminals". In most Packet stations our computer
is employed as a terminal. A terminal consists of a display screen and keyboard
and a connected to an RS-232 port. When you type on the keyboard data is sent
out of the Transmit Data pin of the RS-232 connector on the terminal. When
Receive Data signals are detected on the RS-232 connector the text is displayed
on the screen.
TERMINAL
EQUIPMENT
Devices,
apparatus and their associated interfaces used to forward data along a Packet
Radio network or to a target Packet station/terminal (DTE).
TEXNET
A
networking node protocol developed by the Texas Packet Radio Society and used
primarily in Texas and the southwest. TEXNET uses a custom three port node which
supports 1200 or 9600 baud modems, as daughter cards. A notable feature of
TEXNET is that it can support a local hard drive using the TEXNET board's
on-board disk controller.
TheNET
This
is a networking software package created by Hans Giese, DFBAU, and supported by
NORD-LINK in Germany. TheNET implements a multi-port, multi-station packet radio
network protocol. The latest release of theNET is the X1J4 revised by Dave
Roberts G8KBB and is burned into a 27C512. TheNET X1J revision 4 series EPROMs
implement a bank-switching technique to enable the use of a larger EPROM thus
allowing more features to be added to theNET nodes. DOWNLOAD the X-1J4 Network
EPROM Node Code for the MFJ-1270C, and TNC2 CLONES.
TheNET
PARMS
TheNET
node EPROM's installed in TNCs, operate using timers and other parameters that
are burned into the EPROM. Most of these parameters may be modified over the air
by the SNO. A complete description of these parms are detailed elsewhere in this
book.
THROUGHPUT
A
measurement of the number of bits, blocks, characters, messages or interactive
transactions passing though a Packet or data communications system. Throughput
is usually a number that describes network performance. Baud rate describes only
the number of bit transitions that leave a transmitter in a second. Throughput
is a statistic that actually shows the delivery of data in a Packet network, end
to end. Throughput is calculated by taking the original baud rate, given in
bytes per second, subtracting the overhead and the time used to traverse the
network. This includes the time lost due to network protocols, the lost time due
to choking and collisions.
TIME
DIVISION MULTIPLE ACCESS (TDMA)
a
satellite communications technique for sharing use of a satellite transponder by
dynamically allocating time slots among its users.
TIME
DIVISION MULTIPLEXING (TDM)
Equipment
enabling transmission of a number of independent signals over a common path by
transmitting them sequentially at different instants of time.
TIME-TO-LIVE
When
a packet is sent from one TheNET node to another TheNET node the packet contains
several bytes of information which are useful at TheNET nodes along the path.
One of these bytes of information is the time-to-live initializer. Each time a
node relays the packet one hop further the time-to-live is decremented one node.
When it decrements to zero the message is discarded. Therefore, if the number of
hops that the packet has to travel (hop) to reach it's specified destination is
greater than the initial time-to-live the packet will never reach its
destination. In addition, if the time-to-live on the return trip is not high
enough an acknowledgment will not be returned.
TINK
The
way Doug Sharp K2AD pronounces "TNC."
TIME-SHARING
The
sharing of use of a processor among multiple simultaneous users.
TNC
Terminal
Node Controller, is the combined modem and packet assembler & disassembler.
The interface device between the computer terminal and RF transceiver. The TNC
assembles and disassembles packets and provides error detection. The TNC's job
is to take text typed on the terminal or computer and store it until the user
hits a carriage return . At that time the text is sent to the destination
station. Each line of text ending with a carriage return becomes a packet and is
stored in the TNC until it can be sent to the destination station (channel
clear).
The
TNC has commands that allow the user to set the timing parameters and install
the operator's callsign. Once the user has installed the licensed callsign, the
TNC adopts its own personality and allows only connect requests directed to the
installed call.
TOPOLOGY
(Network)
The logical or physical arrangement of nodes on a Packet Radio network in
relation to each other. How well a network functions is more related to its
topology (the quality of the links and paths) than to the software used to form
a network.
TRACE
PACKET
(PING)
A special test packet in Packet Radio networks that causes a report to be sent
back to the network control operator who originated the (ping) test packet.
TRAFFIC
Calls
being sent and received over a communications network.
TRANSMISSION
The
electrical transfer of a signal, message or other form of information from one
location to another; most desirably in unaffected form at the receiver.
TRANSMISSION
SPEED
Number
of pulses or bits transmitted in a given period of time, expressed variably in
Bits Per Second (BPS), Words Per Minute (WPM), Characters per Second (CPM), an
occasionally as Lines per Minute (LPM) in WeFAX transmission.
TRANSPARENT
To
make the some forms of binary Packet Radio information invisible to other Packet
operators. In Packet communications, a suspension of control character
recognition in certain systems while information transfer is in progress. This
mode prevents the TNC from reacting to special characters. Another mode of
operation in a packet TNC that allows the sending of all possible binary
characters without fear of actuating commands in the TNC. The transparent mode
is primarily used for the transfer of binary data files.
TRANSPONDER
Generally,
a telecommunications device that receives a signal and relays it in another
form.
TRANSPORT
LAYER
The
fourth layer of the ISO Open Systems Interconnection Reference Model. The
"transport" layer performs the function of end-to-end control of
transmitted Packet Radio information and is responsible for optimized use of the
Packet Radio network resources. It controls the transfer of datagrams between
two level 3 nodes via a number of intervening L3 nodes.
TRUNK
A
Packet Radio or Packet link between two nodes that are used as backbones. The
trunk is normally a limited access path that allows only nodes or system node
operator (SNO) access.
TTL
(Transistor-to-Transistor Logic)
An
internal transfer standard for electronics devices in which a 1 state is +5
Volts and a zero state is 0 volts. Some TNCs will not accommodate this form of
interface. A separate signal converter is required when a TNC does not support
TTL. Some TNCs have built-in TTL strapping options or connectors.
TTY
(TELETYPE™)
The
registered trade name for teleprinters and data terminals of the Teletype
Corporation. Used generically in the telecommunications industry for
teleprinters or data terminals that emulate teleprinter operations.
TURNAROUND
TIME
Time
required to reverse the direction on a half-duplex communications channel.
TVRO
Television,
Receive Only: The acronym is used to denote the home satellite receiving system.
TXData
Transmit
Data stream fed to a modem modulator. (See also, RXData)
TXDelay
The
period of time (usually 350 mSec/TXD 35) when TNC issues a transmit command and
the actual time the packet data stream begins.
U
UA
Unnumbered
Acknowledgment frame. A packet frame sent in unconnected (unproto) mode to
acknowledge a connect or disconnect request.
UART
Universal
Asynchronous Receiver/Transmitter. This is an IC which is used in a computer to
activate a serial port.
UI
Unnumbered
information frame. An Information frame without a frame number that is sent as a
broadcast during a beacon, nodes broadcast, CQ, and other similar frames. It is
not acknowledged and there is no assurance that it will be received.
UNATTENDED
OPERATION
Transmission
automatically controlled or not requiring a Packet Radio operator to function.
UNPROTO - An unproto packet is a packet transmitted without expecting a
response. Technically it is called a UI frame which means Unnumbered
Information. A packet station issuing a beacon for all to see or calling CQ,
would use an Unproto packet.
UPLINK
That
portion of a communications link reaching upward from the Earth to a satellite.
In some Packet nodes (X-1J/X2) the "user" command will display the
uplink and downlink stations.
V
VADCG
Vancouver
Amateur Digital Communications Group. An amateur packet group in Vancouver B.C.
responsible for much of the early development our now widely used packet
protocols. The early version was called; "the Vancouver Protocol."
Much of the amateur packet level 2 protocol was developed in 1979 by Doug
Lockhart VE7APU and the VADCG in Vancouver BC.
VIRTUAL
CIRCUIT
In
a Packet Radio network this term refers to the appearance of a dedicated private
channel or connect. In some types of open radio environments the individual
packets may take alternating routes. The service provided by a packet network
when two stations are in direct connect. Virtual circuit data packets generally
carry less header information than datagrams, since addresses have been
specified at the time of the connect setup. Amateur AX.25 packet at level 2 uses
virtual circuits.
W
WAN
Wide
Area Network: This is a system where many servers and nodes may talk to each
other. This kind of system is rugged in that communications would probably not
be compromised if a single site went off the air. The maior problem with this
methodology is that if the only packet systems available are of this type then
users, which present transient loading, will find that the WAN is unable to
support massive intermittent loads during peak usage times.
WAVEGUIDE
Physical
transmission medium using boundaries of conductors to guide electromagnetic
signals; widely used in microwave radio since WWII; closely akin to fiber optic
light guide operations.
WEATHER
NODE
A
weather station linked to a packet radio node for remote monitoring of weather
conditions by packet radio. TheNET X-1/X-2 node with ADC options support the
addition of windspeed, wind direction, temperature, and rain indicators that can
be read by connecting users.
WEFAX
Weather
facsimile, reconstructed satellite pictures and photographs. The WEFAX receive
mode is now an added feature of the "all mode" digital controllers.
WIDEBAND
A
term applied to facilities or circuits where bandwidths are greater than that
required for voice.
WINDOWING
A
split screen in some computer displays, permitting display of two events
simultaneously. In some Packet Terminal programs (BUXTERM, MULTICOM, PCPakRatt,
etc) the ability to perform type-ahead data in a "split-screen."
WIRELINE
LINK
This
is a connection between a pair (or more) of TNCs such that the TNCs communicate
via their radio ports but without a pair of radios. The modems are bypassed,
thus the TNCs talk at higher data rates than 1200 baud.
WORMHOLE
An
amateur packet circuit between two distant points using commercial communication
circuits such as telephone, satellite or microwave links.
X
X1J4
NODE CODE
Developed
by Dave Roberts G8KBB; The most popular Packet Radio Networking node code in use
today. This program is a derivative of the Nord)(Link TheNET node code but has
many enhacanced features added plus the functionality to enable allows routing
from a TheNET system directly to the Personal mailbox, Personal BBS, BBS,
DXCluster or other Packet programs running on the PC.
The
latest release of theNET is the X1J4 revised by Dave Roberts G8KBB and is burned
into a 27C512. TheNET X1J revision 4 series EPROMs implement a bank-switching
technique to enable the use of a larger EPROM thus allowing more features to be
added to theNET nodes. DOWNLOAD the X-1J4 Network EPROM Node Code for the
MFJ-1270C, and TNC2 CLONES.
X.25
A
CCITT standard protocol for the subscriber interface to a public packet switched
network. Consists of two layers, link (level 2) and packet (level 3). The
amateur AX.25 protocol is a highly modified version of just the link layer of
X.25. X.25 it does not have a packet layer and X.25 is not used in amateur
Packet radio.
XON/XOFF
Software
handshaking using characters such as Crtl-S/Crtl-Q to turn on and off a
communications channel. When the XON/XOFF is defeated with the TNC XFLOW command
set to OFF, the TNC then uses the RTS/CTS signal lines on the RS-232 port to
control data flow thus implementing "hardware handshaking."
Y
YAPP
Yet Another Packet Protocol. A shareware terminal software package to interface a personal computer to a TNC. YAPP contains scrolling, message handling, editing, and other utilities to aid the user on packet. YAPP was written by Jeff WA7MBL
Z
ZIP
or ZIPPED
Data, and other ASCII or Binary files compressed in an encoded manner that enables the data to be stored and transferred in smaller space or less time. Reference is ZIP or WinZip.
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