A shift control circuit includes a first limiter circuit, a phase shifter, a first suppressor, and a reducer. The first limiter circuit limits the amplitude of a control target signal input from a microphone, having undergone A-D conversion by an A-D convener, and frequency differentiation by a pre-emphasis circuit, and having the relative intensity of harmonic components increased. The phase shifter performs, for the control target signal having undergone the amplitude limitation, phase shift on the frequency component within a first frequency range. The first suppressor suppresses, for the control target signal having undergone the phase shift, the frequency component equal to or greater than a second threshold. The reducer suppresses, for the control target signal having the suppressed frequency component, the frequency component within a second frequency range, and outputs as an information signal. A modulator performs frequency modulation on a carrier wave in accordance with the information signal, and a transmitter produces a transmission signal from the carrier wave having undergone the frequency modulation, and transmits the transmission signal via an antenna.