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 uses comparators equivalent to LM339 to generate signals of two waveforms whose...
A Reset-Set flop-flop capable of directly controlling a relay or other power load can be...
The circuit shown here can be used to produce low-frequency sine wave signals from CMOS logic. The...