The present document is based on the principles of terminal adaptor functions presented in the ITU-T I-series of Recommendations (I.460 to I.463).

The PLMN supports a wide range of voice and non-voice services in the same network. In order to enable non-voice traffic in the PLMN there is a need to connect various kinds of terminal equipment to the Mobile Termination (MT). The target of the present document is to outline the functions needed for the terminal adaptation.

The bearer services are described in 3GPP TS 22.002 and the general network configuration is described in 3GPP TS 23.002. The PLMN access reference configuration is defined in 3GPP TS 24.002. The various connection types used in the A/Gb mode or GERAN Iu mode PLMN are presented in 3GPP TS 43.010. Terminology used in the present document is presented in 3GPP TR 21.905 and 3GPP TS 29.990. For support of data services between a PLMN and other networks see 3GPP TS 29.007.

The present document is valid for a 2nd generation PLMN (A/Gb mode) as well as for a 3rd generation PLMN (Iu mode). If text applies only for one of these systems it is explicitly mentioned by using the terms "A/Gb mode" and "UTRAN Iu mode". If text applies to both of the systems, but a distinction between the ISDN/PSTN and the PLMN is necessary, the term "PLMN" is used.

NOTE 1: From R99 onwards the following services are no longer required by a PLMN:

• the dual Bearer Services "alternate speech/data" and "speech followed by data";
• the dedicated services for PAD and Packet access;
• BS 21 ... 26 and BS 31 ... 34.

From REL-4 onwards the following service is no longer required by a PLMN:

• the synchronous Bearer Service non-transparent (BS 30 NT).
• Non-transparent facsimile (TS 61/62 NT) for the A/Gb mode and GERAN Iu mode.

The support of these services is still optional. The specification of these services is not within the scope of the present document. For that, the reader is referred to former releases.

NOTE2 : Please note that the Gb interface does not play any role in the scope of the present document although the term "A/Gb mode" is used.