E.1 Outgoing call in a Mobile-service Switching Centre (MSC)

09.123GPPApplication of ISDN User Part (ISUP) Version 2 for the Integrated Services Digital Network (ISDN) - Public Land Mobile Network (PLMN) signalling interfacePart 1: Protocol specificationTS

If the requested bearer is "speech" or "3,1 kHz", the echo control device indicator is set to "1" (outgoing included) in the IAM sent by the MSC.

An incoming half echo control device is "reserved" on the outgoing circuit of the MSC.

If the backward call indicators parameter received in the ACM indicates that an incoming half echo control device is included, the "reserved" incoming half echo control device of the outgoing circuit of the MSC is disabled.

If the backward call indicators parameter received in the ACM indicates that an incoming half echo control device is not included, the "reserved" incoming half echo control device of the outgoing circuit of the MSC is enabled.

If the requested bearer is "64 kbit/s unrestricted", the echo control device indicator is set to "0" (outgoing not included). No echo devices are reserved.