| 摘要 |
PROBLEM TO BE SOLVED: To suppress power consumption in waiting state. SOLUTION: When this interphone device is in waiting state, a direct current voltage stabilized through a resistor R1 of an indoor master unit 1 is superimposed on a connection line L1 connecting the indoor master unit and an indoor expander 2, and the voltage level of the direct current voltage is detected by direct current detection circuits 17 and 27. Also, when an extension call is made, the voltage level of the direct current voltage is transformed into 0 V due to the control of activated voltage control circuits 18 and 28, a direct current voltage from a power supply is also fed to data transmitting and receiving circuits 12 and 22 due to the control of activated power supply control circuits 19 and 29, and extension call data are transmitted to a connection line. Thus, the power feeding of the direct current voltage from the power supply to the data transmitting and receiving circuits whose operation is unneeded in their waiting state is interrupted so that power consumption in the waiting state can be suppressed.
|
