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.
Found in old English documentation, this circuit simulates a diac and can be used to trigger...
This circuit was obtained from a Radio Electronics from October 1963. The 4 transistors must be...
This didactic circuit was found in a 2001 documentation. It presents the result of programming in binary...