This service description document details the Inband Signaling (IS) protocol between Transcoder/Rate Adapter Units (TRAUs) for speech traffic channels for the Tandem Free Operation (TFO) of speech codecs, sometimes also termed "Vocoder Bypass". It is applied to the cdma2000^®1 standards.

Annex A 4 standards. is mandatory and defines the capability and requirements used in the development of this TFO 6 standard.

Annex B is mandatory and describes the general IS protocol, which is applicable to TFO specifications for all systems (e.g., TDMA, cdma2000, GSM and UMTS)

Annex C is informative and gives the rules for In Path Equipment (IPE). It is identical for all systems (e.g., TDMA, cdma2000, GSM and UMTS).

¹ cdma2000^® is the trademark for the technical nomenclature for certain specifications and standards of the Organizational Partners (OPs) of 3GPP2. Geographically (and as of the date of publication), cdma2000^® is a registered trademark of the Telecommunications Industry Association (TIA-USA) in the United States.