Converting data to a format suitable for transmission by a Fixed Cellular Terminal (FCT)

摘要

A telecommunications apparatus comprises a wired telephone (5) connected to a Fixed Cellular Terminal (1), which connects the telephone. (5) to the PSTN via a wireless link. DTMF tones generated by the telephone cannot be reliably transmitted over a voice channel of the wireless link, so they are converted to signals compatible with the V.18 protocol (15,23) and then to signals compliant with the Cellular Text Modem (CTM) standard. Optionally the DTMF tones can be converted straight to CTM signals. The subscriber line interface circuit (SLIC,7) detects when DTMF pulses are present on the input from the telephone, and opens switch (9) to direct the pulses to the processing circuitry (15,19,21,23), which otherwise remains closed if normal voice communication only is input. Applications inlcude telecare systems connected to a remote monitoring centre.