ETSI TS 127 003 defines Terminal Adaptation Functions (TAF) which are integrated in a Mobile Termination (MT) and which enable the use of synchronous bearer services in the PLMN and the attachment of Synchronous synchronous Terminals terminals to an MT (see 3GPP TS 24.002 [3]). For the case where asynchronous terminals are attached to the TAF when using synchronous bearer services in the PLMN, the reader is referred to 3GPP TS 27.002 [36] for the asynchronous MT-TAF interface specifics and to the present document for synchronous bearer service specifics on the TAF-IWF interface. The general aspects of Terminal Adaptation Functions are contained in specification 3GPP TS 27.001 [9]. The present document covers support of synchronous data services (see 3GPP TS 22.002 [6]) for the following interfaces and procedures:

• V.22 [15] DTE/DCE Interface;
• V.22 bis [16] DTE/DCE Interface;
• V.26 ter [19] DTE/DCE Interface;
• X.21 bis [24] DTE/DCE Interface;
• X.32 [30] Procedure;
• V.25 bis [18] Procedure;

NOTE: From R99 onwards the support of 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 support of the following service is no longer required by a PLMN:

• the synchronous Bearer Service non-transparent (BS 30 NT).

the Teleservice Facsimile non-transparent (TS 61/62 NT) for A/Gb 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 GSM R98 or R99 respectively.

NOTE: 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. GERAN Iu mode is for further study.