AT&T MERLIN LEGEND Installation & Maintenance Manual page 146

Installation
Fault Location Filter (a factory-installed option)
Note: Before the CSU can be installed, the serving telephone
company must be contacted to obtain all necessary information,
such as services available, equipment options, and power on the
line. Also a completed "Request for 1.544 Mbps End Section
Characteristics" form must be submitted to the telephone
company.
Follow these procedures to install the components of the
551 T1 L1 CSU.
Set the Switch Options on the Signal Monitor Unit and the
Office Repeater
Set the switches before placing the Signal Monitor Unit (SMU)
and the Office Repeater (OR) in the CSU chassis.
The default settings accommodate most installations. However,
some options depend upon local line conditions, for example,
availability of line power and the type of service requested by the
customer.
Also, proper settings for some options must be obtained from
AT&T, its authorized representative, or the local telephone
company. The local telephone company representative must be
informed of the options selected.
Signal Monitor Unit Switch Settings
There are four option switches in the SMU (see Figure 25). These
switches govern the operation of the following options:
ONES causes the unit to transmit an "ALL ONES" keep-alive
signal to the CO when the customer signal drops below the
minimum average ones-density.
3-38 Channel Service Unit