| 摘要 |
PURPOSE:To prevent continuous power supplied from an external power source due to the malfunction or the like of a telephone set for which power is supplied from the external power source only when processing is required. CONSTITUTION:At the arrival of an off hook signal or an incoming signal, a power holding circuit 9 controls external power from a battery 6 or a power supply part 7 is so as to supply it to a telephone set for a fixed time. A CPU 1 for controlling the telephone set starts processing simultaneously with the supply of the external power, sends an external power supply extending signal to the circuit 9 within a fixed time, and after the end of various processing, sends an external power supply stop signal to the circuit 9. When the CPU 1 runs away, an external power supply stop signal is outputted from a watchdog circuit 12 for monitoring the CPU 1 to the circuit 9, so that external power supply to the telephone set is stopped. Thereby even if malfunction is generated in the telephone set by any reason, external power supply is not continued thereby preventing useless power consumption. |
