This circuit cuts the audio for a few seconds between words, which allows ads to be detected, since this does not occur in music. The circuit is a from Radio Electronics Experimenter from 1989.
This circuit came out in an English publication of 1976, but it can be easily assembled using...
When light fails to focus on the sensor, a common photo-transistor, the relay closes its contacts....
This traditional clock circuit with common CMOS components with discrete logic functions was found...