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Glossary 83
Glossary
AMI
(Alternate Mark Inversion) a line coding method for T1 spans.
bandwidth
the difference between the highest and lowest frequencies in a given range; the maximum data-
carrying capacity of a circuit. (Greater bandwidth indicates higher speed data-transfer.)
B8ZS
(Binary 8-Zero Suppression) a line coding method for T1 spans
channel
an increment of bandwidth provided by the WAN.
channel bank
a voice time division multiplexer.
CSU
(Channel Service Unit) the interface to the T1 line that terminates the local loop.
Drop-and-insert
a service feature where some number of DS0s are passed through the T1 Modem Bank to other
telephone equipment, usually a PBX. The remaining DS0s terminate at the T1 Modem Bank.
DS-0
(Digital Signal Level 0) a 64K bps channel, the world-wide standard speed for PCM digitized voice
channels.
DS-1
(Digital Signal Level 1) in North America, a 1.544M bps data stream composed of 24 DS0 channels. A DS1
is provided on T1 transport facilities.
DSX-1
(Digital Signal Cross Connect, Level 1) part of the DS-1 specification.
DTMF
(Dual Tone Multi Frequency)touch-tone dialing
E&M
Signaling leads on a voice tie line; known as “Ear and Mouth.” Types I and II are most common in the US.
EPC/X
(Enhanced Performance Concentrator)
ESF
(Extended Super Frame) ESF is based on ANSI T1.403 or AT&T Pub 54016.
flow control
a mechanism for limiting the amount or rate of data sent by a transmitting entity to avoid congestion
in the network or the receiving device.
ground start
T1 supervision and signaling method
ISO
(International Standards Organization) a voluntary, independent organization chartered to define international
standards for communications of all types.
ISO model (
More completely, the ISO model for Open Systems Interconnection) This is the model of computer
communications that has seven layers. The ISO model describes the ISO OSI communications architecture. ISO
communications standards fit into several places in this model.
jitter
short term variations in the rate at which data arrives on the T1 span. Jitter is removed by means of a “jitter
attenuator” which is present in the T1 Modem Bank.
LAN
(
Local Area Network) a communications architecture that passes information between multiple systems
over relatively short distances at high speeds
line
the physical interface to the WAN.
LBO
(Line Build Out) Insertion of loss in a short transmission line to make it act like a longer line
Loop-Start
T1 supervision and signaling method
modem
(
Modulator-demodulator) a device for modulating a carrier with a data stream ready for transmission and
demodulating or extracting a data signal from a received signal.