| 摘要 |
The pre-alarm system is provided for an anti-theft alarm where a signal from a displacement/vibration detector is picked up by a one-shot timer circuit. If no other activation signal is picked up after the first signal is received, a main control alarm circuit is activated for driving a siren circuit to generate a short chirp sound as an audible warning. A flashing circuit emits a light signal for a preset period of time as a visible warning. If the number of activation signals received subsequent to the first are greater than a predetermined threshold number, or the activation signal continues for a predetermined period of time, the main control alarm circuit is activated for driving, the siren circuit to give a normal audible signal alarm, and both, the flashing circuit for flashing a light and the dome light control to provide visible signals. |
