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.
In this circuit of a 1975 publication, a silicon transistor is used as a sensor. We can employ a...
This circuit was found in a 1978 publication. Equivalent operational amplifiers can be used. The...
The great advantage of the circuit shown in the figure is the fact that its frequency is...