03.533GPPService descriptionStage 2Tandem Free Operation (TFO)TS
Tandem Free Operation: corresponds to the Mobile-to-Mobile calls for which the speech is not transcoded two times but only one by the Mobile Stations.
For the purposes of the present document, the following abbreviations apply:
TFO: Tandem Free Operation
IPE: In Path Equipment
Further abbreviations used may be found in GSM 01.04