FAIL_SAFE_TIMED_ALARM

Published:2009/6/30 1:53:00 Author:May | From:SeekIC

Horn comes on about 30 s after intruder closes door switch by opening car door. Delay is produced by NE555 timer to allow driver to close door after entering or leaving. Thief must keep door open to get leg room for removing equipment under dash. Diodes are 50-PIV 1-A silicon. K1 has 12-V coil. Alarm is set at all times. S1 is normally dosed pushbutton type in door jam. Opening S1 starts timer, and closing it resets alarm.-R. S. Harvey, Junk Box Foils Thieves, QST, Sept.



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