Home appliance anti-theft alarm circuit

(1) Circuit working principle The circuit principle is shown in the figure.
VTH, Ri and SB form a thyristor trigger switch circuit; JC1, Brother,
VT1, VT2 and BL form an analog siren circuit. Normally, SB is
pressed by household appliances, causing its two normally closed contacts to disconnect, VTH is blocked without a
trigger signal , and the alarm does not work. When household appliances are moved
. The two contacts of SB are automatically closed, and the trigger end of VTH passes through R. The trigger signal is obtained from the
positive electrode of the power supply , rrH is turned on, and IC1 is energized to work. The siren acoustic signal output is amplified by VT1 and VT2, driving the speaker to emit a loud alarm sound. At this time, even if the appliance is opened back to its original position or the SB is destroyed, the alarm sound cannot be stopped. Only when the owner turns on the switch S installed together with the alarm and is difficult for others to find , can the alarm be released.