Description
Here is a simple but effective burglar
alarm circuit that can be fixed on windows to detect break through. The
circuit uses a fine wire element fixed as a network through the window
glass for sensing the break through . Normally the base of Q1 is held
to ground potential by the wire element.So Q1 will be off and SCR H1
will not be conducting,and horn will be off.When the wire element is
broken the base of Q1 will be raised to positive potential, Q1 will be
on and so SCR H1 (TYN 612) will be ON making the horn to blow and this
condition will be latched by the SCR.The circuit remains ON until the
normal condition is restored or the power supply is switched OFF.
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