Avaya 03-300430 User Manual

1. Loop transmit to receive on the system side.

Remove the transmit signal from the TN722, TN767, or TN464 circuit pack inputs and 
outputs and loop it around to the receive signal going toward the TN722, TN767, or TN464 
circuit pack at the first unit wired to the TN722, TN767, or TN464 circuit pack. 

The loop-around signal may take different forms depending on the installation.

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In some cases, the unit connected to the system may provide a switch or a terminal 
interface to control the desired loop around. Make sure that the signal is looped toward 
the system and that the timing signal is looped.

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In most cases, it may be necessary to temporarily rewire connections at the 
cross-connect fields to loop the signal back toward the switch.

The point at which the signal is looped should be one at which physical access is easy and 
where the signal level is within the line compensation (i.e. equalization) range of the 
hardware connected. A few cases exist where access to the loop around cannot be easily 
provided at locations where the signal level is within the line compensation range of the 
hardware. Use change ds1 location to change the line compensation. 

2. Execute test board location for the TN722, TN767 or TN464. Look at results of Test 

#144, the Slip Alarm Inquiry test. When this test fails, the error code gives the number of 
slips detected since the last Slip Inquiry test was run. If the test fails, run it at least one more 
time to ensure that slips have occurred since the loop around was installed.

A timing loop exists when a system receives timing from another system whose timing 
reference is directly or indirectly derived from itself. The system synchronization planner must 
avoid creating a timing loop when administering the synchronization references in a system. 
Timing loops can lead to loss of digital data between systems that are exchanging data with any 
system within the loop. An invalid timing signal will also be generated by any system within the 
loop, thus propagating the invalid timing signal to any system(s) using a system within the loop 
as a synchronization reference.
A correctly designed network has no loops, and each piece of equipment in the network is 
supplied by a clock with an equal or lower stratum number. (For example, the inputs to a 
Stratum-3 clock should never be from a Stratum-4 device.) 

CAUTION:

Synchronization administration changes should never be done without consulting 
the network’s overall synchronization plan. If you suspect that synchronization 
administration changes are needed, follow normal escalation procedures.