This 1968 Mallory circuit uses an uncommon integrated circuit today. The circuit has a 30 to 20,000 Hz response with lower power and is powered by 12 V.
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...