A hopping control device selects one hopping pattern out of hopping patterns P1 to PN, reads out a hopping frequency sequence arranged in the selected hopping pattern from a frequency hopping pattern memory, and sends the hopping frequency sequence to frequency synthesizers as a frequency designation signal by wire at a predetermined period. The frequency synthesizers generate local oscillation signals of a frequency specified by the frequency designation signal, respectively, and output the local oscillator signals to mixers, respectively, to thereby perform communication by a frequency hopping system between a first housing unit and a second housing unit.
