| 摘要 |
PURPOSE:To always obtain a constant DC voltage, by converting a share of voltage drop at a power receiving terminal according to the change of a communication cable length into a frequency output, and transmitting it to a power supplying terminal. CONSTITUTION:A voltage controlled oscillation circuit 158 supplies the output of an oscillation frequency corresponding to a voltage drop value supplied corresponding to the length of a communication cable 104 to an audio frequency modulation part 134 via a lowpass filter 159. Therefore, in the output of the audio frequency modulation part 134, a frequency modulated component corresponding to the share of voltage drop in the communication cable 104 is included in addition to a voice signal. In a master device 100, the frequency modulated output of sound from a slave device 102 side and the share of voltage drop at a sound demodulation part 122 is demodulated, and frequency-voltage conversion is performed at a frequency-voltage conversion part 129b, and the DC power in which the share of voltage drop is compensated by a variable voltage regulator 128 is outputted to the power supplying terminal A.
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