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.
This circuit was found in documentation from the 1980s. The transistor depends on the desired...
This circuit was found in the magazine Sperimentare 4 of 1977 and can be easily assembled using TIC...
This simple circuit was found in Popular Electronics from the 1980s. The circuit uses an LED as an...