| 摘要 |
PURPOSE:To confirm whether a communication line is normal or not at any time by providing a main controller consisting of a DC power source and a transmission-reception part which sends a signal on multiplex basis to the DC power source, the communication line connected to the transmission-reception part of the main controller, and a repeater with a display part which is powered on by the DC power source. CONSTITUTION:When a signal is sent out of the transmission-reception part 2 of the main controller 1, the signal is sent through the communication line 10 applied with a DC voltage on multiplex basis and transmitted to terminal equipment 9 through an information outlet 4. The terminal equipment 9 performs demodulation through a modem part 7 and various kinds of control through a control 8. The information outlet is made nonpolar by using a diode bridge 6 and the display part 5 made of a light emission diode is turned on. If the communication line 10 is short-circuited or broken, the display part 5 turns off to warn the abnormality to be outside. |
