| 摘要 |
PURPOSE:To prevent system-down for a long time by detecting a fault of mis- transmission protecting circuit momentarily and using a control signal so as to stop the start of a transmitter when the mis-transmission protecting circuit interrupting the transmission of the transmitter using squelch interrupting a reception output is failed in the absence of a reception input of a receiver. CONSTITUTION:When a radio wave from a preceding station is lost, an output (b) of a receiver 10 is zero and a transmitter driving signal (c) is also zero and a transmitter 20 stops its transmission. Then a monitoring output (e) for the transmitter 20 is zero and the original state is set. In the case of a fault, even when the reception output (b) is zero, the transmitter driving signal (c) is not zero and consecutive 1s take place in the monitoring output (e) for the transmitter 20. In this case, the output (f) of an EX-OR gate 5a goes to 1 in a fault discrimination section 32 and the output (h) of an inverter INV goes to 0. Thus, the output (c) of an AND gate 3a goes to 0 to stop the transmission of the transmitter 20 forcibly. Thus, even when the AND gate 3a of a transmitter starting control section 31 is failed and the transmitter 20 results in the consecutive transmission state, the transmission is momentarily stopped forcibly. |
