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.
November 2016 - Maxim's MAX30003, an Analog Front End (AFE) for biopotentials with clinical grade...
This receiver was found in the Radio Electronics magazine of March 1953. It tunes to the medium wave...
Audio signals can be produced by this circuit. Frequency range is determined by C1 and adjusted by...