| 摘要 |
PURPOSE:To detect power supply interruption of a data terminal device at a data supervisory station by giving a detection signal of power supply interruption to a transmission/reception terminal of the data terminal device to fold back transmission data. CONSTITUTION:Transmission data is transmitted to a telemeter device 7 of a data terminal device 3 from a telemeter device 4 of a data supervisory station 1 via an MODEM5, a transmission line 2-1, a contact circuit 11, and an MODEM8, and each response signal is transmitted to the device 4 of the supervisory station 1 via a transmission line 2-2 of opposite route from the device 7. When an external power 12 is failed, a relay RL10 is interrupted and a contact circuit 11 of the RL10 connects the transmission lines 2-1 and 2-2 in loop. Then the transmission signal is folded back at the circuit 11 to the transmission line 2-2 and inputted to a detector 6-3 via a filter 6-2 of a filter 6-2 of a power supply detector 6-3. A detector 6-3 detects the coincidence between the transmission signal transmitted via the filter 6-1 and a reception signal via the filter 6-2 to decide it as the power supply interruption. |
