| 摘要 |
PURPOSE:To monitor a fault on an A/D transmission line continuously by signal processing at a reception side without transmitting and receiving a control signal between a transmission and a reception side, by detecting the switching control period of the A/D signal of the transmission side by the state change of an output signal of detection of a pilot signal. CONSTITUTION:An analog signal 1 and a digital signal 2 are generated by analog and digital pilot signal generating circuits 106 and 107, and are alternated at a constant period T in an A/D converting circuit 104 by a control signal 3 from a switching control circuit 105 to be transmitted from a transmitting circuit 103. This signal is received by a receiving circuit 108, and is branched to pilot detecting circuits 111 and 112 for analog and digital transmission through a demodulating circuit 109 for analog transmission and a demodulating circuit 110 for digital transmission. Then, state change signals 5 and 6 from those circuits 111 and 112 are applied to a phase comparing circuit 116 and the 1st and 2nd change point detecting circuits 113 to detect a switching control period, thereby monitoring a fault on an A/D transmission line continuously. |
