| 摘要 |
PURPOSE:To evaluate immediately a trouble section on a transmission line by sending a false signal to execute the angle modulation with an inherent frequency to the reproducing relaying device of an intermediate repeating installation instead of an input signal and detecting the modulating frequency of the false signal in which the angle of a terminal station repeating installation is modulated. CONSTITUTION:An input signal 11 is sent through a terminal station repeating installation 31 to a transmission line l1. A transmission line signal is reproduced and relayed by repeating installation 511 and 521 included in intermediate repeating installation 41 and 42 and an output signal 21 is outputted from a terminal station repeating installation 32. At the time of turning off the input signal, an input signal turning-off detecting circuit 9 sends a detecting signal to a switching circuit 10, sends a signal executed by an angle modulator 11 for a false signal 12 instead of the input signal with the pilot signal of a pilot signal oscillator 13 of the frequency inherent to a repeating installation 5 toward a transmission circuit 8 and sends it to a transmission line l. An angle modulating detecting device 6 always supervises whether or not the pilot signal oscillator 13 included in the repeating installation 5 is obtained from the presence or absence of the angle modulation of the repeating installation 5 and the modulating frequency.
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