Telecomms Glossary
Telecomms Glossary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #
Select the first letter of the word from the list above to jump to appropriate section of the glossary. If the term you are looking for starts with a digit or symbol, choose the '#' link. Many terms contain Hyperlinks to approriate sites. New terms are added !
Acoustic Coupler
This is a
special cradle in which you place the handset of a phone.
This is connected to a modem, and the modem accesses the
phone line through this coupler. Modern modems connect
directly to the phone line.
Analogue
Analogue refers to
signals that can represent an infinite range of numbers,
as opposed to digital which can only be distinct whole
numbers. Analogue data often comes from measurements,
like a sine wave. The sound a modem makes over the phone
is analog since it can be any of a number of different
frequencies. The fixed-line networks usually transfer
analogue data and fax. The GSM networks are Digital.
ANSI
ANSI graphics
is a set of cursor control codes which originated on the
VT100 smart terminal. Many BBS's use these codes to help
improve the sending of characters to communications
programs. It uses the escape character, followed by other
characters, which allows movement of the cursor on the
screen, a change of color, and more.
Archie
A program and
database which locates files on the Internet.
ARPANET
From ARPA
(Advanced Research Projects Agency) and network. An early
experimental network.
ASCII
American
Standard Code of Information Interchange. It uses 7 bits
to represent all uppercase and lowercase characters, as
well as numbers, punctuation marks, and other characters.
ASCII often uses 8 bits in the form of bytes and ignores
the first bit.
ASCII transfer
When a text
file is sent directly as it is, without any special
codes.
Asynchronous
Transmission
Transmission method in which the intervals between
transmitted characters may be unequal of length.
Transmission is controlled by start and stop bits at the
beginning and end of each character. This way, if there
is line noise, the modem can find out right away where
the next byte should start. [See Synchronous communication].
AT command
Any
instructions sent to a modem that begin with
"AT". See also Hayes
AT command set.
AT command set
See Hayes
AT command set.
Attention
characters
The letters
"AT", which get the modem's attention that you
are about to send it a command. [See also Hayes
AT command set].
Auto Reliable
The ability
of a modem to be able to communicate both with modems
that do have error-control and/or data compression, and
those that do not.
Bandwidth
The
difference between the upper and lower limits of a band.
A range of radio, audio, or other frequencies. Since it
is so limited, a modem must carefully change data into
sounds that "fit" within this range. Similar to
frequency spectrum. Bandwidth of a voice channel is
3000Hz-300Hz which equals 2700Hz. Telephone lines have a
bandwidth from 300 hertz to 3400 hertz.
Baud
A term
referring to the speed at which modems communicate.
Technically, it is the number of changes in an electronic
signal per second. Since the number of changes used to be
the same as the number of bits sent or received per
second, bps and baud are often used interchangeably.
However, there is a difference, which is very often
confused. For example, many 1200bps modems were
advertised as 1200 baud, even though they operate at 600
baud. They send out 2 bits 600 times a second, which
means that it is 600 baud. However, since it is so often
misunderstood, you can assume that when you see
"baud" it means bits per second, unless it is
stated otherwise. The term comes from the scientist J. M.
E. Baudot. [See also bps].
BFT
Binary File
Transfer
Billion Rand
What it costs
to start a cellular network
Bit
A Binary
digIT. It is a number in base 2 (binary), which means
that it can only be a 0 or a 1. It is used in the
expres-sion `bits per second'. [See also byte].
bps
Bits Per
Second. The transmission speed of most modems is measured
in baud or bps. Bps is literally the number of bits sent
by the modem every second. [See also baud].
byte
A group
of 8 bits. It usually represents one character.
CCITT
Consultative
Committee International on Telephones and Telegraphy.
Used to set standards for modems. Replaced by the ITU.
Card
Services
DOS and
Windows 3.1x users must have Card Services enabled to use
their computer's PCMCIA slot(s). Card Services simply
allows DOS/Windows 3.1 to see and set up the computer's
PCMCIA slot. They will automatically allocate a
Communications Port (COM 1 to 5) when the Option modem is
plugged in. The Option modem can then be accessed by
communications programs via the Windows 95-assigned COM
port. Windows 95 users DO NOT need to
install Card Service as it is built into Windows 95.
Notebook users using DOS/Windows 3.1 usually have the
Card Services software bundled with their purchase.
Option modems come packaged with a PC Card Installation
disk that has an install program for these Card Services.
You can however download it here.
Carrier Detect
The
information as to whether or not the modem senses a
carrier, like a fixed-line dialling tone or a data/fax
services enabled on a GSM subscription.
CIS
Card
Information Services. A PCMCIA setup protocol.
Carrier Detect Threshold
A way of
measuring how well a modem can detect valid data over
noisy phone lines. It is measured in negative dBm's
(decibel-milliwatts). The bigger the number (the more
negative) the better. For example,45 dBm is better than40
dBm.
CLIP
Caller Line
ID Presentation. A code that is sent over the phone lines
in some areas when a person makes a phone call. This code
includes the phone number of the person making the call.
Some modems are able to understand this signal, and let
you know who is calling you before you answer the phone.
CLIR
Caller Line
ID Restriction. The ability to block someone who you're
calling from seeing your number.
CDPR
Cellular
Digital Packet Radio
Cell
The
receiver/transmitter a GSM phone connects to; the
equivalent of the base station of a cordless phone. A
cell can support a number of simultaneous calls.
Checksum
A number that
represents a larger group of numbers in order to check
for errors in data transmission. It is commonly used when
downloading a program, as well as in error control
protocols. The checksum is the result of a mathematical
equation, such as adding all the numbers in a block
together (although it is usually more complex than
that).
Chip Set
A group of
important IC chips on a modem (or other computer
peripheral) that are all made by the same manufacturer.
While there are many companies that make modems, there
are only a few that make the chips for them. Because the
chip manufacturer is making the chips for many companies,
they produce more chips, and the price of the chips is
lower than if each company produced their own. This
decreases the price of the modems on the market.
CDMA
Code Divison
Multiple Access. A digital cellular technique invented by
Qualcomm.
CMOS
Complementary
Metal Oxide Semiconductor. A chip which uses small
amounts of electricity. It is used typically on
battery-powered computers and to save configuration
information on other computers when they are turned off.
Communications
program
A program that controls a modem, and has features that
allow the user to do such things as upload, download,
etc. It is similar to a terminal program but more
sophisticated. An example is Trumpet WinSock for
connecting to the Internet, and Windows HyperTerminal.
Compatible
When one object can work just like another. Although the
term is usually used with computers, it is often used
with modems. Many modems are compatible with other
popular modems.
Compress
To make data
take up less space. Archiving programs do this, which
means that files will take less time to transfer with
modems. Many modems now have the ability to automatically
compress the information they send and receive. [See also
archive, data compression].
DAA
Data Access
Arrangement. A device used to connect modems to the
switched telephone network.
Data over GSM
Send digital
data over the digital GSM networks. Click here for a tutorial on data and fax
transmission over GSM.
dBm
Decibel
refers to one milliwatt. This is used to measure certain
levels, such as transmit level.
DSA
Data Services
Adapter, an alternative interface to PCMCIA for
connecting to a fax or data terminal. The Siemens S1 uses
a DSA
Digital
A system
using discrete numbers to represent data. In computer
systems, these are the numbers 0 and 1 (for binary). [See
also Analogue].
DTE
Data Terminal
Equipment. This is computer equipment which is not
directly responsible for communicating, for example, the
computer itself and printers. [See also DCE].
DTMF
Dual Tone
Multi-Frequency. This is used in tone dialing. It is a
method where 2 distinct tones are sent for each digit
dialed.
DTR
Data Terminal
Ready. The DTR signal is sent from the computer to the
modem, to let the modem know that the computer is ready
to communicate.
EDI
Electronic
Data Interchange. Commonly transferred by Internet or
X.400 networks
EEPROM
Electrically
Erasable Programmable Read-Only Memory
EFF
Electronic
Frontier Foundation. An organization promoting civil
rights in cyberspace. It is leading the fight against the
US government's Clipper Chip.
Error Correction
Error
Correction. The ability of a modem to notice errors in
transmission, and to resend incorrect data. [See also MNP 1-4, LAPM, V.42].
E-mail
Electronic mail. Messages that are sent to individual
people. You choose who to send the message to and only
that person receives the message.
ESPRIT
European
Strategic Program for Research in Information
Technologies.
Error
When there is line noise and one or more characters are
changed. This is especially noticeable when downloading
or uploading a program. In this case the error must be
detected, and the data must be re-sent.
FAQ
Frequently Asked
Questions. Click here or on the FAQ icon for the Option
Communications FAQ page.
Firewall
Computer
security that attemps to keep crackers out.
Flame
To write
emotional remarks on electronic mail.
Flow
control
A method of
controlling when information is sent. One method is
Xon/Xoff, where a BBS will send information until your
computer sends an Xoff (CTRL-S). It will resume sending
information when you send an Xon. [See also Xon/Xoff, CTS/RTS].
Full Duplex
A channel
providing simultaneous transmission in both directions.
Group III FAX
The standard
controlling fax communication.
GSM
GSM
originally stood for Groupe Speciale Mobile but has been
anglicised to Global System for Mobile Communications, an
international digital cellular standard. South Africa was
one of the first to implement Phase 2 of GSM.
Click here for a brief history of GSM.
Half Duplex
A channel
which signals in both directions, but not simultaneously.
Handover
What occurs
when a cell phone used in a car moves out of the range of
one cell and needs to connect to the next available cell.
The preceding cell then hands over the connection to the
stronger cell.
Hayes AT command set
This is
the set of commands used to operate Hayes modems and
Hayes compatible modems. Almost all of the commands start
with AT.
Hayes compatible
Any modem
which operates in the same way as the modems developed by
Hayes.
Hertz
A unit of
frequency, which equals cycles per second.
Interactive Manual
A
Windows-based modem control and diagnostic program
bundled free with each Option 2-in-1 modem. Here you can
alter all Hayes AT commands using icons! Just click on the
appropriate icon, and the Interactive Manual will
instantly alter the modem's settings. You can also change
the modem's settings to conform to the PTT specifications
of different countries.
ISO
The International
Standards Organisation, the body responsible for setting world
technical standards. It is based in Geneva, Switzerland.
Lotus
Famous for the Lotus 1-2-3 spreadsheet of the 1980's, and
more recently for it's Notes Groupware system. Bought by
IBM in 1995.
Modulation
A process whereby
a signal is transformed from its original form into a
signal that is more suitable for transmission over the
medium between transmitter and receiver.
Mosaic
A GUI
(Graphical User Interface) for accessing the hypertext
WWW (World Wide Web) on the Internet.
MNP
Microcom
Networking Protocol. Error control and data compression
techniques, created by Microcom, that many newer modems
use. They are built into the modem, unlike software error
correction in file transfer protocols. There are
different MNP levels. Levels 1-4 are error control
protocols, and level 5 is a data compression protocol
that can compress data to about 50% of its original size.
A modem with MNP-5 also has MNP-4. MNP 1-4 is also
included in the ITU
V.42 error correction system.
MNP normal mode
This is the
more common mode used with modems that have MNP capability, where the speed from
the computer to the modem can be higher than the
connection between the modem and the remote modem. This
mode uses buffering to prevent lost data.
MoU
Memorandum of
Understanding, the GSM
body that overseas GSM standards and implementation
around the world. It comprises operators and some
manufacturers.
Modem
A MOdulator
DEModulator computer peripheral which allows a computer
to communicate over telephone lines. This is the heart of
computer telecommunications. The main factor that
differentiates modems is their speed, measured in bps.
Analogue modems talk to one another by converting digital
info from the computer into tones called PSK’s. An
ordinary analogue modem cannot be physically connected to
a GSM phone because networks will not
carry PSK tones.
N
NCAIR
National
Center for Automated Information Research.
Network
Operators
The folks who install
and maintain GSM
cellular networks. Click here to see a list of GSM operators around the world. Click here to see the South African network operators.
Non-Transparent
Cellular Data
Non
Transparent phones use a special error correction
technique called RLP. Transparent phones data not incorprate the
RLP error corerction techniqure and their data MIGHT be
corrupted.
PCMCIA
A credit card
sized card that generally plugs into a notebook computer.
It conforms to the Personal Computer Memory Card
International Association spec. Now known as PC
Cards.
PSTN
Public
Switched Telephone Network. This is the regular phone
lines that just about everybody uses.
Pulse
dialing
A method that
some phones use to dial numbers. It involves a series of
"clicks." Most modems support this type of
dialing, which is the only type available in some remote
areas. The other method of dialing is tone dialing.
RJ-11
This is a
normal phone jack. The older South African plugs have a
3-prong connector. All Option modems sold in South Africa
have this RJ-11-to-3-prong adapters.
RTS
Request To Send. This is when the computer tells the
modem that it wants to send information to the other
computer. It is only used in half duplex mode. [See also flow
control, CTS].
Serial Transmission
A method of
transmitting data in which bits are sent sequentially.
SIG
Special Interest Group. The GSM MoU has many SIGS.
SMS
Short Message
Service will display a pager-like 160 character message
in the LCD panel on the phone. Your phone must support
SMS.
To send a FREE SMS message to a Vodacom (082) or MTN (083) subscriber, click here.
Streaming
When data is sent
continuously, without waiting to make sure there are no
errors. Transparent mode on GSM is an example of a
streaming method faster than non-transparent mode, but
unreliable.
T1
Trunk 1. A
heavy duty telephone line.
T3
Trunk 3. A telephone
trunk line.
TDMA
Time Division Multiple
Access, the magical technique used by the digital GSM network to squeeze more calls onto
one channel by dividing a calling channel into a few
"discontinuous" pieces.
Telecommunication(s)
This word has no
precise definition, but is frequently used. Its
definition ranges from "any form of communication
over a distance" to "any communication by
electric means" to "two computers 'talking' to
each other via modems." Methods of communications
that probably are considered telecommunications:
telephones, cellphones, TV's and fax machines. The word
is used both in singular and plural.
Telecommuting
The idea of
company employees working from home, rather than their
office. At home, they can communicate with the office
(and other entities) by modem or voice calls.
TELNET
A program
which lets you access other computer systems through
Internet.
Terminal
Emulation
When a
communications program can simulate the operations of a
smart terminal.
Tone Dialing
This is a
method that a phone or modem can use to dial a phone
number. It uses one audible tone per digit to be dialed.
UART
Universal
Asynchronous Receiver/Transmitter. This is a device in a
computer or modem that will change serial data (the way
data comes in over the phone line) to parallel, and vice
versa. [See also serial, parallel, 16550 UART, 8250 UART,
16450, 16550 UART]. Option high speed modems have a built-in
16550 high-speed UART.
V.17
The ITU standard for
fax transmission at 14,400bps.
V.21
The international
standard, created by ITU, that controls transmission at
300bps.
V.22
The international
standard for transmission at 1200bps, created by ITU.
V.22bis
The international
standard, created by ITU, that controls data transmission
at 2400bps.
V.23
The ITU protocol for
transmission of 1200bps one way, 75bps the other way.
V.24
This, combined with
V.28 is the ITU standard equivalent to EIA's RS-232C
standard. V.24/V.28 has 25 pins, just like the original
RS-232C standard.
V.28
Part of V.24.
V.29
The ITU standard for
9600bps half-duplex communications.
V.32
The international
standard controlling transmission at 9600bps. It was
created by ITU. It has provisions for fallback, if the
line is too noisy.
V.32bis
The international
standard for 14,400 bps modems, ratified by the ITU.
V.34
The international
standard for 28,800 bps modems, ratified by the ITU.
V.42
A standard error
control system created by ITU that is in use on many
9600bps modems and some 2400bps modems. It includes LAPM,
as well as MNP 2-4.
V.42 compatible
This is a modem that
follows all the V.42 specifications, except for LAPM
error control (instead it uses MNP).
V.42 compliant
This is a modem which
follows all the V.42 specifications, and uses LAPM error
control if possible. Otherwise, it will go to MNP error
control.
V.42bis
A ITU standard for
data compression. It can compress data with about a 3:1
compression ratio, although it can compressup to 4:1
given the right conditions. Any modem with V.42bis also
has V.42 error control. [See also Data
Compression].
WWW
World Wide Web. A
hypertext system set up on the Internet.
Waffle
A DOS program
to perform UUCICO.
Winsock
A Windows
subroutine library that provides access to the Internet
TCP/IP.
WINSOCK.DLL
The actual
file containing Winsock.
X.25
This is a packet-switching protocol developed by ITU. It
is used to carry large amounts of data at fast speeds
over leased phone lines.
X.32
This is ITU's 1984 update of X.25, also known as X.25
dialup.
X.400
This is the ITU
standard protocol for a global system for the exchange of
electronic mail.
X.500
The ITU standard for a
directory of the users of the X.400 system.
Xmodem
A file transfer
protocol developed by Ward Christensen around 1977. It is
fairly slow by today's standards, but was the first
widespread file transfer protocol. It uses blocks of 128
bytes, and after each block is sent, it sends a 1 byte
checksum to check for errors. If an error is encountered,
the block will be re-sent. Almost every communications
program offers this protocol.
Xmodem/CRC
The same as Xmodem,
but it has a 16-bit CRC instead of the checksum, which
makes it more reliable (it catches more errors).
Xmodem-1K
This is similar to
Xmodem/CRC, except it uses blocks of 1024 bytes, rather
than 128. It is faster than Xmodem, since it needs to
stop less often to check for errors. This is sometimes
incorrectly called Ymodem. [See also protocol, Xmodem,
Ymodem].
Xoff
The CTRL-S character. This is often used to pause
information that is being sent. The information will be
continued when an CTRL-Q is received. [See also flow
control, Xon].
Xon
The CTRL-Q character. This will sometimes continue paused
information.
Xon/Xoff
The flow control
method using the Xon and Xoff characters. It is built
into the software, not the hardware.
ZIP
The file
extension which refers to archives that were created by
the program PKZIP. You need the program PKUNZIP to get
the files out of the archive.
Zmodem
A file
transfer protocol which is known for its speed, as well
as the ability to transfer information about the files
which it sends. It has crash recovery and auto-download
features, and can use a 32 bit CRC, which makes it almost
error-free.
8-N-1
The most common modem format. "8N1" describes
the way that your computer and the remote are connected.
The first digit is normally 7 or 8, the number of data
bits. The second character is a letter describing the
parity (N for None, M for Mark, S for Space, O for Odd,
and E for Even). The last number is the number of stop
bits. Data is sent as follows: Start bit (0) 7 or 8 bits
of data (parity bit, if used) stop bit (1) (gap bits, if
used)
10BASE-T
An ethernet
connection that uses UTP (unshielded twisted-pair)
wiring.
16550
UART
This is the
UART used with most newer computers and high speed
modems. There are several variations, but they all
include one main feature: they include buffering, so that
if data comes in or is sent faster than the
computer/modem can accept it, the UART will hold the data
(up to 16 bytes) until the computer/modem is ready for
it.
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Specifications subject to change without notice. E&OE.
This page serves merely as an informational aid &, unless stated, does not imply any endoresment of or by the parties mentioned within.
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