This Technical Standard (TS) describes the minimum performance requirements for the Cellular Text Telephone Modem (CTM) for reliable transmission of text telephone text via the speech channel of cellular or PSTN networks. The transmitting parts of the Cellular Text Telephone Modem are specified in [1].

CTM is a general technology, independent of text telephone types. The tests are made only for one specific type of text telephone, the Baudot type. The tests are applicable only to a combination of a Baudot codec and CTM and tests the combined performance. A bit-exact implementation of the CTM transmitter as well as an example implementation of the remaining functions of such a combination are provided in [2].

The test scripts and test vectors required to perform this testing are included in a supplement, which is located in the ziparchive ctm_testing.zip. The path and file names given in this specification refer to the file structures associated with this supplement. A second supplement (zip archive ctm_score.zip) provides the scoring program that is described in clause 6.