When ATER or ABIS cut off, you can have this alarm.
extract of NED:
Calls have been cleared three successive times on the same Abis interface
channel due to BTS and transcoder unsynchronisation.
Supplementary information fields
1 identifier of the base station
2 identifier of the TRX
3 identifier of the radio time slot
4 number of external PCM circuit
5 time slot of external PCM circuit
6 sub-time-slot of external PCM circuit
Lock the channel in question with the MML command ERS.
Check the transmission between the BTS and the BSC (and transcoder).
Check other active alarms concerning the BTS and the BSC
(and transcoder) transmission or transcoder plug-in units.
Correct the faults causing the alarms.
When the above-mentioned transmission alarms have been cancelled
or when transmission is working again, unlock the channel in
question with the MML command ERS.