This circuit that appears in other points of this section and on this website serves to activate a lamp in the event of a power failure. This version is from 1967 documentation by General Electric.
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...