We found this circuit in the October 1988 Radio Electronics magazine. The circuit is still current due to the components used, and changes can be made.
In the figure we have a typical detector stage for a radio receiver. The circuit is from 1963,...
Found in a 1968 Texas Instruments documentation this circuit uses an SCR from that time. Modern...
This circuit was obtained from an American publication of the 80's. The integrated circuit is of the...