This circuit uses common components at the time of its publication in the 1980s. The circuit can be made with modern equivalent transistors. The input signal is sinusoidal.
This Vox or sound activated relay was found in an American documentation from 1975. Equivalent...
This circuit is from Motorola's Linear Interface ICs from 1993. The circuit uses a booster...
The existence of field effect transistors at the input of the integrated circuit (operational...