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