| 摘要 |
PROBLEM TO BE SOLVED: To simply transmit digital data in a duplex system. SOLUTION: Serial data are outputted from a signal output terminal of a digital data signal source 10, a level conversion circuit 111 converts a signal level of the serial data and the converted data are fed to an FSK modulation circuit 112, where FSK modulation is applied to the data. The frequency of a carrier is, e.g. 11 MHz and 13 MHz and they respectively correspond to a level '1' and a level '0' of the digital signal. A driver 113 amplifies the modulated signal and the amplified signal is coupled with a human body through a capacitor whose capacitance is abut 100 pF. When the human body is in contact with an electrode 170, the modulation signal transmitted through the human body is amplified by a preamplifier 151, demodulated by a demodulation circuit 152, a comparator 153 applies waveform shaping to the demodulated signal, a level conversion circuit 154 converts the level and the resulting signal is fed to a serial input terminal of a receiver 20. The transmission/reception is conducted by a half duplex system.
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