A transmission circuit, mounted on a printed board and having attenuation characteristics, to attenuate an amplitude of a reception signal according to the attenuation characteristics, and to transmit the amplitude-attenuated reception signal, as an attenuation signal; and a correction circuit, mounted on the printed board and having correction characteristics, to attenuate an attenuation signal that has been received from the transmission circuit according to the correction characteristics, and to transmit the attenuation signal attenuated, as a correction signal are provided. The attenuation characteristics are such characteristics that the ratio of the amplitude of the attenuation signal to the amplitude of the reception signal decreases as the frequency of the reception signal increases. The correction characteristics are characteristics with which the ratio of the amplitude of the correction signal to the amplitude of the attenuation signal increases as the frequency of the attenuation signal increases.