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This is a simple but
effective alarm circuit which can reset its self after a time that
you select. it has normally open and normally closed triggers
which make this circuit very practical. This alarm has normally
open and normally closed triggers. It's on a 555 timer so the
alarm will reset it's self after a certain amount of time. The
time is adjustable with the variable resistor in the circuit. The
alarm has a reset switch which you can replace with a key switch
to make it more secure, and you can change the triggers to other
types of door or window switched too. The alarm uses a relay which
is connected to a siren but you can replace the siren with
whatever you want. The circuit is running off 9VOLTS but can range
from 4V - 16V.
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