| 摘要 |
PURPOSE:To realize a remote control of a device just by a pair of telephone circuits, by providing an automatic telephone switchboard having a circuit for connection of a booster power supply included in a subscriber circuit to a telephone circuit and a circuit which detects the presence of connection of the telephone circuit to the booster power supply to the telephone side, respectively. CONSTITUTION:A subscriber circuit 17 of an automatic telephone switchboard is provided with a capacitor 9, DC power supplies 7 and 15, a call signal generator 14, etc. A detecting part 18 contains a telephone 1 connected to a telephone circuit 5, a photocoupler 3 and a Zener diode 4 and then detects that a booster power supply is connected to the circuit 5. A control part 19 includes a control circuit 21 which supplies the output signal of the part 18 via a filter circuit 20 to control a circuit 22, a power supply 23 and a device 22 to be controlled. Then, it is possible to perform a remote operation of the device via a pair of telephone circuits only through the circuit 17 and with combination of binary signals showing two state in which both relays 11 and 13 are working together and either one of these two relays has no working. |
