| 摘要 |
PURPOSE:To reduce power consumption when communication is not performed and to economize a terminal device by supplying power to a communication control part, which controls transmission and reception between a master device and the terminal device even when communication is not performed and supplying power to the other parts through a transmission line when a communication request from the master device is received. CONSTITUTION:A communication control part 11 in a terminal device 1 is always fed by a storage battery 14 which is floatingly charged by a commercial power source 3, and a principal circuit 12 is fed through a power-on switch 13 by the power source 4. When communication is not performed, a master device 3 stops transmission of a carrier wave to a transmission line 2. When the carrier wave does not come from the transmission line, the control part 11 sets the switch 13 to the open state. When the device 3 transmits the carrier wave to the transmission line 2, the control part 11 detects the carrier wave coming from the transmission line 2 to set the switch 13 to the close state. As the result, the circuit 12 is set to the communicatable state. Thus, the power consumption is reduced when the communication is not performed, and the economization of the terminal device is improved. |
