| 摘要 |
PURPOSE:To discern service interruption of a slave station in a master station by adding circuits for using a service interruption detection signal receiving device of master station side in common with all slave stations. CONSTITUTION:A scanner 9 is working slways in a master station, and input circuits of a service interruption detection signal receiving device 10 are connected cyclically as No. 1 slave station A No. 2 slave station B No. 1 slave station A.... For instance, if service interruption occurs in the No. 1 slave station, voice frequency of (f2-1) band comes to the scanner 9 for a specified time. When an input circuit of the service interruption signal receiving device 10 is formed by the scanner 9, (f2-1) is received and a slave station number signal from the scanner 9 is added and stored. An alarm is indicated at the same time. When service interruption is restored, a data transmitting device (1-1) operates and a demodulator (5-1) detects (f1-1). This signal is taken into the scanner 9 and memory of service interruption detection in the service interruption signal receiving device is erased. |
