ADTRAN 1202060L2-1, Руководство пользователя

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1202060L2-1 TSU LT User Manual 1-1
Chapter 1
Introduction
T1/FT1 OVERVIEW
T1 digital communication links have been used by the
telephone companies (telcos) for voice transmission since the
early sixties. The D4 channel bank is an example of a T1
digital carrier system that was introduced in the mid-
seventies and is still widely used by the telcos.
Communication demands of businesses continued to grow to
the point that the telcos began offering T1 service directly to
the public. D4 channel banks began to be used for T1 in
corporate network topographies for voice. The technological
advances in computer development also created a demand
for T1 data communication which now is a large part of the
T1 traffic.
T1 Service Offerings
T1 is a digital service that is delivered to the user over two
pairs of wires from the service provider. The signal operates
at 1.544 mega bits per second (Mbps) and is usually extended
by repeaters that are installed about every mile after the first
6000 feet. The T1 signal is divided into 24 time slots or digital
signal level zeros (DS0s) which operate at 64 kilo bits per
seconds (kbps). Each time slot is occupied by digitized voice
or by data.