| 摘要 |
PURPOSE:To perform excellent signal transmission at all times by measuring a noise level and a reception level at a receiving station and sending them to a transmitting station, and controlling its amplification degree at the transmit ting station according to the information. CONSTITUTION:A slave station 6 passes a sent signal from a master station 1 through a band-pass filter 15, measures the reception level S by a level measur ing instrument 23 in the idle section of the signal, and measures the noise level N in a period where the signal is not sent and inputs it to a CPU 18. This CPU 18 makes the measurement result into data and adds the measurement information to a response signal to be sent to the master station 1. This response signal is modulated by a transmission part 21 and sent out to a power distribution line 3 through a coupler 4. The master station 1, on the other hand, modulates the response signal by a transmission part 21 and inputs it to a reception part 13 through a coupler, and also inputs it to a CPU 6 through a demodulator 12. The CPU 6 sends the gain control command to a gain control ler 22 according to the sent measurement information and control an SN ratio to larger than a reference value.
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