| 摘要 |
PROBLEM TO BE SOLVED: To permit judgment between whether the connection has failed or the battery has been removed by a thief, by detecting stoppage of power supply with a power supply stop detection means and inputting it to the CPU, starting operation of a timer means, giving an alarm when a reference time is due. SOLUTION: With a set switch 6 ON, anti-theft function of a CPU 14 starts operation. In the case that a battery 1 is removed after turning on the set switch 6, when the CPU 14 is reset, if voltage supplied to the CPU 14 gradually decreases to become smaller than the reference value of 4.5 V, a 5 V detection circuit (power supply stop detection means) 12 detects it and switches over to the high level for supplying the CPU 14. At this time, a 5 V charge/discharge circuit (timer means) 13 gives an alarm for removal of battery 1 if it judges that more than a reference time has lapsed since start of the discharging. On the other hand, when the CPU 14 is not reset, the system does not judge that the buttery is removed, thus evading an alarm. |
