Verilink T1 ESF CSU (34-00309.B) Product Manual - Manual (Page 21)

Test Jacks 9
T1.403 / 54016 PLB Unloop: The unit supports T1.403 FDL
payload loopback unloop command messages (00110010
11111111 repeating).
Test Jacks
The bantam jacks located on the left side of the unit provide
signal access as follows:
The FROM NET and TO NET jacks can be used to break the
network connection to the T1 ESF CSU internal circuitry and
connect the network to a piece of test equipment.
The NET MON and EQ MON jacks are used for passively
monitoring received signals passing through the unit (between
the DTE and the network).
The FROM EQ and TO EQ jacks can be used to break the
equipment connection to the T1 ESF CSU internal circuitry and
connect the equipment to a piece of test equipment
NOTICE: When connected to the TO EQ and FROM EQ jacks,
the EQ LOS indicator lights. This is due to the test connection
and is not an indication of signal loss from the equipment.