Pulse code modulation (PCM) circuits such as T1 and E1 trunks, may have fault conditions; when these occur, alarm signals are used to report the fault. These alarm signals are defined in the PCM specifications (ITU-T G.732 and ITU-T G.733).
When a signaling process registers with the capability SL_SIGPROC_CAPABILITY_TRUNK_ALARM, Blueworx Voice Response notifies the signaling process when a PCM fault condition occurs or when a PCM fault condition is cleared on any of its trunks. Blueworx Voice Response notifies the signaling process of a PCM fault condition by sending the SL_TRUNK_ALARM_REQ primitive, with the slAlarm field set to indicate the fault. Blueworx Voice Response notifies the signaling process that a PCM fault condition has cleared by sending the SL_TRUNK_ALARM_REQ primitive with the slAlarm field set to SL_ALARM_CLEAR.