Found in an 80's Hands On Electronics, this circuit turns on a light when it gets dark and goes out when it gets dark. The circuit can be adapted to use high-brightness white LEDs.
This basic Schmitt trigger was found in an American publication from 1968. The circuit uses...
This circuit is from an American 1964 documentation. Transistors of the time are used, but modern...
This simple circuit uses small speakers for both listening and speaking (microphone). The feeding is...