| 摘要 |
PURPOSE:To decrease the capacity of an input switch, by connecting an input part to the low level side of a voltage reduction transformer for electric power as well as a signal output part via a relay contact which is closed when a signal is transmitted. CONSTITUTION:A signal of about 20A is injected to the low level side of a pole transformer 8 of 6.6kV/210V by a transmitter 9 for answer-back signal which injects a coded current signal of FSK of 450+ or -15Hz to a distribution line. The transmitter 9 is provided with an input switch 11, a DC power supply circuit 12, an inverter circuit 13 which generates a signal frequency of 450+ or -15Hz, a coupling circuit 14, a relay contact 15 which is closed only when the signal is transmitted, and a control circuit 16 which controls the relay 15 and the inverter 13. The signal output current does not pass through the switch 11 since the contact 15 is connected to the power supply side of the switch 11. Thus the size of the switch 11 can be reduced. |
