To enable two kinds of bidirectional simultaneous call transmission at least with prescribed band width by enabling the simultaneous multiplex use of frequency inside an applied network and using low-speed digital voice coding.

The receiving function of base station is essentially inverse to a transmitting function. Digital voice information from a PBX 15 is inputted to a CODEC 16. Then, four pieces of CODEC 16 belong to a VCU 17 and perform voice compression to the time slots of respective frequency channels. Then, a CCU 18 controls a TDMA function, extracts the transmission channel output of CODEC 16 of correspondent VCU 17 and transmits data to a modem 19 in proper format at the rate of 16k symbols/sec. An IF signal modulated by the modem 19 is converted to an RFUHF signal by an RFU 21 and sent through an antenna interface 22 to a transmission antenna. An RPU 20 is a central processing unit for transmitting connection data and control messages to the CCU.