| 摘要 |
PURPOSE:To decrease a power current without varying a pattern of a low voltage alarm and to extend a time to reach a circuit operation limit voltage after low voltage alarm ringing by decreasing the duty of a drive signal of a driver only on the occurrence of a low voltage. CONSTITUTION:When a voltage of a battery 11 reaches a prescribed voltage or below, a low voltage detection control circuit 20 controls a duty control circuit 16 based on a timing control signal so as to allow a signal generating circuit 15 to generate a signal at the duty of low voltage alarm. A signal of a low voltage alarm pattern is inputted from a low voltage alarm pattern generating circuit 14 to the low voltage alarm generating circuit 18. A low voltage alarm generating signal subjected to pattern processing by the low voltage alarm generating circuit 18 is inputted to a driver 8 via a changeover circuit 19 and the driver 8 drives a speaker as an annunciating means to generate a low voltage alarm tone different from a call tone. Thus, a power current is decreased on the occurrence of a low voltage alarm and a time to reach a circuit operation limit voltage is extended after the occurrence of low voltage alarm. |
