CCITT Rec. Q.118 (11/1988) – SPECIAL RELEASE ARRANGEMENTS
4.3.1 Answer signal not received by an outgoing exchange after receiving a number-received signal or number-received ...
4.3.2 Delay in clearing by the calling subscriber in automatic service (arrangements made in the outgoing country)
4.3.3 Clear-forward signal not received by the incoming exchange after sending a clear-back signal