This circuit is from Radio Electronics from March 1985. The circuit uses common components at the time and LEDs as indicators. The power supply is 9V.
This circuit was obtained from an American 80's documentation. The balanced mixer can be shown in...
This circuit was found in a 90s Electronic Engineering. The quadruple operational amplifier can be...
I found this circuit in an English publication from 1989. This configuration can be mounted with...