| 摘要 |
PURPOSE:To enable an equipment to be miniaturized, to be set in a portable shape, and to be fitted for transmission/reception at a narrow band area, by connecting a circuit that outputs a signal in which an audible frequency signal is modulated by an ultrasonic wave, to the circuit that converts an inputted ultrasonic wave to the audible frequency signal, and converts it to an acoustic signal. CONSTITUTION:A transmission/reception switching circuit 2 is connected to the ultrasonic vibrator 1b of a transmitter-receiver 1. At the preceding stage of a transmission power amplifier 4, a modulator 6, and an audible frequency signal input means 7 are connected in series, and also, at the succeeding stage of a demodulator 5, a power amplifier 8, and an electric-acoustic conversion means 9 that converts an electrical signal to a sound wave, are connected in series. Therefore, it is possible that a person who carries an ultrasonic transmitter-receiver inputs a bit of information from the audible frequency signal input means 7 by a human voice, or the operation of a readout command switch, and sends out the ultrasonic wave from the transmitter-receiver 1, or receives the ultrasonic wave inputted from another ultrasonic wave transmitter- receiver from the transmitter-receiver 1, and receives the bit of information in sound from a earphone, or a speaker.
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