| 摘要 |
<p>PURPOSE:To decide accurately a fault of radio receivers connected in parallel by using an output of a fault decision circuit and a reply timing signal to polling. CONSTITUTION:A master station 1 and slave stations 31, 32...3n make communication by the polling system via radio lines 41, 42, 43...4n and a radio relay device 2. When outputs of two sets of receivers 24-1, 24-2 connected in parallel differ, a receiver fault decision circuit 25 gives an output and inputs it to one input of a gate circuit 50. A reply timing signal generation circuit 51 generates a reply timing signal delayed at the end of a transmitter start timing signal 52 appearing at the transmission of a polling signal and inputs the signal to the other input of the gate circuit 50. When input signals exist at both the inputs of the gate circuit 50 at the same time, the circuit 50 gives an output to start an alarm circuit 29. Then a fault of the receiver is decided accurately without causing alarm at the reception of an undesired radio wave.</p> |
