| 摘要 |
PURPOSE:To obtain a communication system which transmits a single burst signal which is natural in terms of time by comparing and deciding on the frequencies of signal detection of two demodulators without using any test signal, and thus obtaining switching information. CONSTITUTION:While both demodulators A and B decode a message signal normally, a signal appears at the output of neither inhibiting circuit INH13 nor 13' and an up/down counter 14 goes neither up nor down. For example, when a switch 11 selects a demodulator side A, no control pulse 108 is generated and only a pulse 108' is inputted in case of the occurrence of a function fault of the demodulator A, so the circuit INH13' generates an output to put the counter in subtracting operation. Said operation is repeated and when the value of the counter decreases below a lower limit value, a signal A-ALARM for the fault of the demodulator A is generated and a switching output circuit 16 sends out a control signal 112 to operate the switch 11, selecting the output 109' of a demodulator B. |
