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.
We found this precise crystal oscillator for the 144 MHz band, depending on the crystal used. The...
We found this circuit in a 1981 publication. We applied an audio signal, for example, a music...
In the figure we have a simple circuit to measure the current in an electronic device and thus...