This circuit was found in the October 1989 issue of Radio Electronics magazine. It drives an auxiliary relay with the call signal for a possible louder bell.
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...