To enable high-speed modem signals to be communicated correctly between a mobile station and a base station, without garbled data in a PHS.

Analog modem signals, inputted through a telephone circuit, are coded into digital signals by a 14 or 16-bit linear CODEC, the coded 14-bit (or 16-bit obtained by adding two bits) or 16-bit digital signals are divided into channel data which are 4 bit each, and the digital signals are sent to slave mobile stations through the four different channels (channel 1, channel 2, channel 3, and channel 4) on radio transmission. The slave mobile station integrates the coded data, which are divided into the four channel data that are 4 bit each, into the coded data of 14 or 16 bit, and then converts them into analog modem signals through a data decoding process by a 14 or 16-bit linear CODEC. Using such a setup, since analog modem signals are sent or received without being subjected to a data compression process by the use of ADPCM, the data are never spoiled.