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Installation
Chapter 2
After unpacking the unit, immediately inspect it for possible shipping
damage. If damage is discovered, file a claim immediately with the
shipping carrier; then contact the ADTRAN Customer and Product
Service (CAPS) department (see inside back cover for information).
For proper operation of the Express L768, only suitably
approved and certified wall plug power supplies with
ratings of 12 Vdc, 800 mA, 9.6 watts should be used.
SDSL NETWORK CONNECTION
T1 Overview
The T1 digital communications link has been used by telephone com-
panies (telcos) for transmitting voice since the early sixties. The D4
channel bank is a T1 digital carrier system that was introduced in the
mid-seventies and is still widely used by telcos. Communication de-
mands of businesses continued to grow to the point that the telcos be-
gan offering T1 service directly to the public. D4 channel banks began
to be used for T1 in corporate network topographies for voice. The ad-
vances 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 Mbps and
is usually extended by repeaters that are installed about every mile af-
ter the first 6000 feet. The T1 signal is divided into 24 time slots (DS0s)
which operate at 64 kbps. Each time slot is occupied by digitized voice
or by data.
61203192L1-20
Express L768 User Manual
2-1
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