This Vox or sound activated relay was found in an American documentation from 1975. Equivalent transistors can be used, and the SCR can be a TIC106. The relay is according to the supply voltage.
Found in a 90s documentation, this circuit triggers the SCR when there is an overvoltage in order...
The presented circuit makes use of operational ones that are not common in the market. More modern...
In the figure we have a monostable that is activated with switch S1 and pressed for an instant. The...