| 摘要 |
The invention provides an antitheft system comprising an alarm unit 1 attachable to a commodity, and an antitheft gate 2 installed in the vicinity of an exit of a store and having incorporated therein a transmitting circuit for producing an alarm activating signal for the alarm unit 1. The alarm unit 1 comprising a buzzer 1, receiving antenna 15 and control circuit 18. The control circuit 18 comprises an interrupt detecting circuit 18b alternatively settable in an interrupt permitting mode wherein the signal received by the antenna 15 is permitted to pass through the circuit 18b or an interrupt prohibiting mode wherein the received signal is prevented from passing therethrough, and a CPU 18a for judging whether the received signal input from the interrupt detecting circuit 18b is the alarm activating signal. The CPU 18a activates the buzzer 11 when the received signal is the alarm activating signal, while setting the detecting circuit 18b in the interrupt prohibiting mode for a predetermined period of time when the received signal is not the alarm activating signal. This suppresses shortening of the life of battery due to useless power consumption of the alarm unit 1.
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