Glossary Terms - "A"
Access Charges
Fees paid by subscribers and long-distance carriers for their use of the local exchange in placing
long distance calls.
Access Line
A line assigned a specific telephone number that connects a customer's phone or related instrument
to a central office.
ACD (Automatic Call Distributor)
A system that handles incoming call traffic, sending calls to the first available station within
predefined groups. If all stations are busy then a recorded message is played and the call is put
in queue until a station becomes available.
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.
Alphanumeric
A generic term for alphabet letters, numerical digits, and special characters which are machine-
processable. Describes a character set containing both letters and digits, and usually, addition
characters such as punctuation marks and other symbols.
Alternate Routing
Routing a call or message over a substitute route when a primary route is unavailable for immediate
use.
Ameritech
One of the seven Regional Bell Holding Companies (RBHCs) resulting from divestiture, covering the
midwestern U.S., based in Chicago, and comprised of Illinois Bell, Indiana Bell, Michigan Bell,
Ohio Bell, and Wisconsin Tel.
Analog
A transmission method using continuous electrical signals, varying in amplitude or frequency in
response to changes of sound, light, position, etc. impressed on a transducer in the sending unit.
The description of the continuous wave or signal (such as the human voice) for which conventional
telephone lines are designed.
Analog transmission.
The traditional telephone technology in which sound waves or other information are converted into
electrical impulses of varying strengths or amplitudes.
ANI (Automatic Number Identification)
Ability of the network to notify the called party of the calling party’s number and/or directory
listing.
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.
ASR
An Access Service Request is a formal request for another company to provide facility access for
the requesting companies traffic. This request includes information on trunk level, connection
meet points and service activity.
Asymmetrical
A term applied to certain modems that use the majority of the bandwidth on a dial-up link for
data transmission in one direction, and a small portion of the bandwidth for control information
traveling in the opposite direction.
Asynchronous
A transmission method in which information is transferred one discrete character at a time and is
delineated by a start and stop indicator at the beginning and end of the character. This way,
if there is line noise, the modem can find out right away where the next byte should start.
The opposite of asynchronous is SYNCHRONOUS transmission.
ATM (Asynchronous transfer mode)
Not the money machine! This is an international CCITT standard for high-speed [broadband]
packet-switched networks that operates at digital transmission speeds above 1.544 Mbps.
Based on frame packets not cell packets. This communications protocol specifies how diverse
kinds of traffic are transformed into standardized packets which can be managed uniformly within
the network.
Attendant
An operator of a PBX console or telephone switchboard.
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