| 摘要 |
PURPOSE:To eliminate a system down state and to improve the reliability of a system by providing two earth stations and sending a pilot signal when one station detects a signal break while the other sending a pilot signal. CONSTITUTION:When an opposite station sends the pilot signal, this station confirms that by the lamp illumination of a pilot signal receiver 3 and turns on an SW 1. The pilot signal is received right after that, so a reset signal is inputted to a timer 4, so a time-out state is not entered and no pilot signal is sent. If the pilot signal of the opposite station is ceased, the receiver 3 receives no pilot signal, no reset signal is inputted, and the timer 4 counts up the time. A time-out signal is outputted unless the pilot signal is received within the time-out time, the S-side input of an FF 5 is turned on, and the output is turned on, so that an SW 2 is turned on. Consequently, the pilot signal is sent through a synthesizer 2 connected to a pilot signal generator 7. The opposite station recovers from the abnormality during this period.
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