Alarm Circuits


Posted on Feb 7, 2014

High Power Siren Circuit This article is all about a comparatively strong siren circuit useful for any purpose. A complementary transistor pair (BC 557 & 337) is arranged as an oscillator, directly drives the speaker. Transistor Q1(BC 557) is used to provide full charging of capacitor C2. When P1 is pressed, C2 discharges through R8 and


Alarm Circuits
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the circuit starts oscillating at a low frequency that increases slowly until a high frequency steady tone is reached and it is kept. When P2 is released C2 starts discharging and and output frequency slowly decreases. When C2 is charged fully the circuit stops oscillations. Tips. Adjust the




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