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 high-gain circuit uses junction FETs (JFETs) and must be powered by somewhat high voltages. The...
This circuit counts 1 per second, displaying the value in binary. The circuit is TTL and must be...
Critical components of this project are the Geiger tube and the 300V battery. The battery can be...