This is an amplifier from the 70s. The integrated circuit used is uncommon today and the power supplied is not the greatest. The circuit is from Motorola.
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...