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, obtained in a 1983 magazine, can drive loads up to 100 mA if the transistors are...
It is possible to design a monostable multivibrator around a voltage comparator of the four...
This voltage inverter circuit is from a Radio Eklectronics from October 1965. It was used in...