| 摘要 |
PURPOSE:To balance an injection voltage level of a mark signal and that of a space signal injected to a distribution line even when an impedance of the distribution line differs from the mark signal and the space signal respectively because of the difference from the frequency of the mark signal and the space signal of a frequency shift modulation signal injected to the distribution line. CONSTITUTION:A converter circuit 1a outputs an output Ea in response to the setting by a setting circuit 2a to which a voltage level in response to the frequency of the mark signal is set. On the other hand, a converter circuit 1b outputs an output Eb in response to the setting by a setting circuit 2b to which a voltage level in response to the frequency of the space signal is set. When an inverter control circuit 40 outputs a frequency command C of the mark signal to an inverter circuit 3, a transistor(TR) 7a is conductive and when the inverter control circuit 40 outputs a frequency command C of the space signal to the inverter circuit 3, a transistor(TR) 7b is conductive. Thus, the output of the converter circuits 1a, 1b is adjusted so that each signal outputted to the distribution line 6 via a coupling circuit 5 has an equal voltage level.
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