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.
This circuit was found in an Electronics World magazine from 1990. The circuit can be mounted...
We found this circuit in an old RCA publication. The components are of the time, admitting...
This circuit was found in the ON Semiconductor's Thyristor manual of the 1980s. The high quality...