PURPOSE: To attain stable dialing with less electric interference by using two dial ICs assigned for a power failure time and a power application time and operating selectively them in response to the state of power failure or application of power.
CONSTITUTION: Two dial ICs 1A, 1B are provided to a dial circuit and either of them is started selectively in response to the state of power failure or application of power. That is, an operating voltage +5v in the operating voltage +5V obtained from a commercial power supply AC 100V through an AC adaptor and an operating voltage V obtained from a telephone line is lost at power failure, then a power failure/power application changeover circuit 3 informs the operating condition of power failure or power application to the dial ICs 1A, 1B depending whether the state is power failure or application of power according to the circuit operating output in response to the voltage change. Thus, the dial ICs 1A, 1B are selected depending on the power failure or application of power. Thus, accurate and sure dialing corresponding to each state is implemented and current consumption is reduced.
MURAYAMA TADASHI
OONAKAHARA SATOSHI
