| 摘要 |
PURPOSE:To eliminate a failure in communication due to environmental conditions of weather, etc., a load state, etc., by increasing an amplification degree a specific time after the reception level of a signal at an opposite station drops below a level at which demodulation is possible, and performing retransmission automatically. CONSTITUTION:Code signals 1, 0,... that a CPU 1 sends are supplied to a power distribution line 6 through a modulating device 2, an amplifier 3, and a coupler 5 and sent to the opposite station. The opposite station demodulates and receives the signal, and modulates and sends a response signal to the power distribution line 6 as a carrier signal. This response signal is inputted to a demodulator 7 through the coupler 5 and inputted to the CPU 1. If the reception level of the opposite station drops below the threshold level of the demodulator owing to weather conditions, etc., and the response signal from the opposite station is not received by the CPU 1 within a certain time, a gain control command is sent out the specific time later and the gain of the amplifier is raised to a specific level by a gain controller 8, thereby resending the signal.
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