Investigation on DID/DOD interface circuit in trunking communication system

This paper introduces a useful direct inward dialing/direct outward dialing (DID/DOD) interface circuit in a trunking communication system, which is controlled by a single-chip microprocessor. The double tone multi-frequency encode/decode circuit and voice integration circuit provides 2/4 wire conversion, voice indication, and DTMF code transmission and reception. The DID/DOD interface circuit provides the automatic access to voice and data communication between the radio subscriber and PABX/PSTN subscriber in a mobile communication system.