Chapter 1. Introduction; T1/Ft1 Overview; T1 Service Offerings - ADTRAN TSU LT User Manual

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Chapter 1

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Introduction

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 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.

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