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 was found in an 80's Electronic Engineering. The circuit uses a multivibrator with...
This circuit was found in a 1960s book of projects by Gernsbak. The circuit uses germanium...
This circuit was found in an American documentation from the 80's. The components are from that...