| 摘要 |
PURPOSE:To simplify the circuit constitution of a SC signal demodulation system by adding a leaked output of an oscillator to a service channel signal (SC signal) subjected to frequency conversion through mixing with an output of the oscillator at a mixer in a transmission terminal station and sending the result to the reception side to eliminate the need for a synchronizing circuit of the SC signal for the reception system. CONSTITUTION:In sending a multiplexed main signal and service channel signal, the inputted SC signal and an output of an oscillator 5 (f5 in oscillation frequency) synchronously with a reference frequency oscillator 8 are mixed with a mixer 6, a leaked output of the oscillator 5 is added and a signal having frequency arrangement as shown in a figure 4 is sent via a transmitter 9. The f5 component is extracted by using a band pass filter having the center frequency f5 from the signal received by a receiver 10 at the reception side of the intermediate relay station, the component is used at the mixer 26 to branch the SC signal from the reception signal. On the other hand, as the inserted SC signal, the f5 component extracted by the mixer 27 is used and the frequency arrangement shown in the figure 4 is used, than the circuit constitution of the demodulation system of the SC signal is simplified. Further, the f5 component is leaked only at the terminal station and not in the intermediate relay station.
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