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Ampere - A unit of measure of electrical current.
AC - see Alternating Current.
Acceptance Angle - The largest angle that a guided ray
of light is accepted by a fiber optic cable.
Access Method - The rules by which a network device
gains the rights to transmit a communication on the network.
Common methods include carrier sense multiple access with collision
detection, token passing, and demand priority.
ACR - see Attenuation Crosstalk Ratio.
Alternating Current - An electric current that
cyclically reverses the direction of flow. Frequency is the
rate at which a full cycle occurs in one second.
Amplitude - The maximum value of a varying signal.
Amplitude Modulation - One of three basic methods (see also
Frequency and Phase Modulation) of adding information to a sine
wave signal in which the magnitude of the signal is varied to
impose information on it.
ANSI - American National Standards Institute
Analog Signal - An electrical signal that varies continuously
without having discrete values (as with a "digital"
signal).
AppleTalk - Apple Computer's networking scheme, integrated
into most Apple system software, that allows Apple computing
systems to participate in peer to peer computer networks and
to also access the services of AppleTalk servers. See also LocalTalk.
ARCnet - Attached Resource Computer Network. A relatively
low speed form of LAN data link technology (2.5 Mbps) developed
by Datapoint, in which all systems are attached to a common
coaxial cable. ARCnet uses a token-bus form of medium access
control in which a system transmits only when it has the token
Asynchronous - Transmission where sending and receiving
devices are not synchronized. Data must carry signals to indicate
data division.
Asynchronous Transfer Mode (ATM) - A form of very fast
packet switching in which data is carried in fixed length units
called "cells". Each cell is 53 bytes in length, with
5 bytes used as a header in each cell. ATM employs mechanisms
that can be used to set up virtual circuits between users, in
which a pair of users appear to have a dedicated circuit between
them. ATM is defined in specifications from the ITU and ATM
Forum.
Attachment Unit Interface - The IEEE 802.3 standard name
for the cable connecting an Ethernet transceiver (MAU) to a
networked device. An AUI cable is equipped with a 15-pin connector
that mates with a 15-pin connector on the networked device.
Attenuation - The decrease in magnitude of a signal as
it travels through any transmission medium such as a cable or
optical fiber. Measured in dB per unit of length.
Attenuation Crosstalk Ratio (ACR) - The difference between
attenuation and crosstalk, measured in dB, at a given frequency.
A quality factor for cabling to assure that signal sent down
a twisted pair is stronger at the receiving end of the cable
than any interference imposed on the same pair by crosstalk
from other pairs.
Audio - Used to describe the range of frequencies within
range of human hearing; approximately 20 to 20,000 Hz.
AUI - see Attachment Unit Interface.
AWG - American Wire Gage-A wire diameter specification.
The smaller the AWG number, the larger the wire diameter. |
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