A transmitter (1) converts an input signal from a microphone (2) into a plural-bit digital signal by means of an A/D converter (4) at predetermined time intervals. An encoder (6) divides the digital signal into plural blocks and adds a parity bit to each block to thereby form a coded signal. A transmitting unit (8) modulates a carrier with the coded signal and transmits the modulated carrier through an antenna (10). A receiver (12) includes two tuning units (18A, 18B). Corresponding coded signals outputted from the tuning units (18A, 18B) are inputted to a decoder (20). The decoder (20) makes a parity check on respective blocks of the corresponding coded signals and selects and outputs an error-free one of the corresponding blocks of the corresponding coded signals.