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Wrong clock cable connection causing loss of syncronization

Publication Date:  2012-07-25 Views:  165 Downloads:  0

Issue Description

We use RTN980 V1R003C00, the CSHN card take the clock from the OSN using Ethernet cable to the  CLK/TOD1 port     in the CSHN then define the external clock as the main clock then enable the SSM protocol and the the other RTN's takes the clock from the STM-1 cable that connected to the RTN 980.

Alarm Information

L_SYNC: loss of synchronization this alarm generated when loss of synchronization o ccurs in the receiving port.

Handling Process

First check the clock synchronization status and found that it is working in the free running mode then check that the external clock is created and the SSM protocol is enabled after founding every thing is created correctly check the cable and repair it  by cnnect the same pair in pin 1,2 at the RTN side and pin 4,5 at the OSN side to be as decribed for the CSHN card and check the synchronization status and found the alarm dissappeared and the status changed to be Normal mode G.811 refrence mode.

Root Cause

The problem was in the connection cable that it was made using wrong pins(1,2 & 6,7) but due to the description of the clock configurations of the CSHN card that for clock cable we use one pair only in the RTN side we put them in pin 1,2(Signal input) in the RJ connector and in pin 4,5 in the OSN side.
 Pin assignments for the CLK/TOD1 port


Working Mode

External Clock


Signal input (-)


Signal input (+)


Not defined


Signal output (-)


Signal output (+)


Not defined


Not defined


Not defined


For CSHN the clock cable we use pin 1,2 in the RTN(receiver side) side and pin 4,5(transmitter clock side) in the OSN side.