This relay triggered by voice or by another sound was found in an Elektor from the 90's. The circuit uses a 12 V sensitive relay and has no sensitivity control.
The PA222 integrated circuit used in this project from an American 1967 documentation is not...
This circuit with an optical path sensor was found in a 1995 documentation. The circuit fires...
This circuit was found in an 80's Electronic Design. It amplifies TTL fast signals for a coaxial...