scope:

This service description document details the Inband Signalling Protocol between Transcoder/Rate Adaptor Units for speech traffic channels for the Tandem Free Operation (TFO) of Speech Codecs.

This service description should be considered together with GSM 08.60 (Inband control of remote transcoders and rate adaptors for Enhanced Full Rate and Full Rate traffic channels) and GSM 08.61 (Inband control of remote transcoders and rate adaptors for Half Rate traffic channels).

Annex A is mandatory and describes the general Inband Signalling (IS) Principle.

Annex B is informative and gives the rules for In Path Equipment (IPE).

Annex C is the formal SDL description of the TFO Protocol as given in clause 10. Clause 10 has precedence in case of ambiguities. A part of Annex C is in electronic format. Annex C is informative. It supports the formal verification of the TFO Protocol.