Cause

The remote device/endpoint/PBX does not respond with an ALERTING/PROGRESS/CONNECT indication within the time administered in the T303 or T310 timers Q.931 specification.

Cause value 18 indicates high traffic conditions in the serving ISDN network or noisy conditions on the T1/E1 span carrying the D-Channel messaging. The noise causes loss of messages sent to the remote device. The remote device is also unable to respond to the incoming SETUP request.

This cause value has end-to-end significance. Communication Manager returns this cause value to the user who has originated the call.