This audio level indicator was found in October 1980 Radio Electronics magazine. See the table with the dB values of the indicated signals.
This circuit is from an American documentation from the 90's. The SCR can be of any type and the...
This sonic relay or vox was found in a Popular Electronics from the 90's. The power MOSFET can be of...
With this circuit it is possible to connect a comparator to a power stage via two wires. The...