Selective Light Amplifier (CB25488E)

This IR light sensor circuit was found in the July 1992 issue of Radio Electronics magazine. It is tuned for 20 kHz modulated light.

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Breathalyzer (CB25160E)
This circuit was published in an article in Radio Electronics magazine in October 1988. It uses...
Simple photometer (CB20507E)
This 3-component circuit uses an analog indicator. We found it in an old publication....
Common Telephone Line Simulator (CB6873E)
This simple circuit can be used to power a simple communication system using ordinary telephones....