Multi-tone alarm circuit

Published:2011/6/25 6:09:00 Author:TaoXi | Keyword: Multi-tone, alarm circuit | From:SeekIC

The multi-tone alarm circuit: the multi-tone alarm circuit is composed of the 555 timer, it can monitor the a, b, c, d points at the same time. In peacetime, the a, b, c, d points are connected with the ground line by wires, the 555 circuit stops working, the speaker is silent. When the invader touches off any one of the channels, the electric potential of this point will increase, the corresponding diode conducts, the 555 circuit starts oscillation, the speaker outputs the alarm. For different monitoring points, the oscillation frequencies are different too, and also the speaker tones.



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