scope:

The telefax group 4 teleservice within the Integrated Services Digital Network (ISDN) is an international service, offered by service providers, enabling subscribers to exchange correspondence either manually or automatically via telecommunication networks.

Subscribers can communicate by means of group 4 facsimile terminals standardised in accordance with the appropriate CCITT Recommendations on an international level.

The basic element of the correspondence between people using the service is the page, as the smallest unit of text treated as an entity. No restrictions shall exist so far as the operator procedures for generation of the text or the positioning of text within the reproducible area on a page are concerned.

As defined in the appropriate CCITT Recommendations (see Clause 2), there are three classes of group 4 facsimile terminals:

Class I: the minimum requirement for class I is a terminal which is able to send and receive documents containing facsimile encoded information (in accordance with CCITT Recommendations T.6 [13], T.503 [1], T.563 [2] and T.400 [10] series).

Class II: the minimum requirement for class II is a terminal which is able to transmit documents that are facsimile encoded (in accordance with CCITT Recommendations T.6 [13], T.503 [1] and T.400 [10] series). In addition, the terminal shall be capable of receiving documents which are facsimile coded (in accordance with CCITT Recommendations T.6 [13], T.503 [1] and T.400 [10] series), teletex coded (in accordance with the basic coded character repertoire as defined in CCITT Recommendation T.61 [9]), and also mixed-mode documents (in accordance with CCITT Recommendations T.501 [11] and T.400 [10] series).

Class III: the minimum requirement for class III is a terminal which is capable of generating, transmitting and receiving facsimile coded documents (in accordance with CCITT Recommendations T.6 [13], T.503 [1] and T.400 [10] series), teletex coded documents (in accordance with the basic coded character repertoire as defined in CCITT Recommendation T.61 [9]) and mixed-mode documents (in accordance with CCITT Recommendations T.501 [11] and T.400 [10] series).

Service requirements contained in this standard take into account group 4 - class I facsimile terminals.