This circuit can be implemented with either TTL or CMOS logic. The speed depends on the logic used and the circuit can be used with microcontrollers, functioning as a shield.
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...