DARL_ALARM

Published:2009/7/15 22:20:00 Author:Jessie | From:SeekIC

This alarm senses darkness. Photocell PCC1 is normally irradiated with light and has a low resistance. In darkness, the resistance increases, and enough bias is available to turn on Tr1, activating the oscillator circuit consisting of IC1 and associated components. This produces a tone in speaker LS1.



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