This receiver was found in a 1924 book by Gernsback. The circuit uses three tubes and is powered by 3 batteries of different voltages, common at the time.
This simple PWM circuit was found in the March 1991 issue of Radio Electronics magazine. The...
This circuit divides the grid 60 Hz frequency to obtain 20 Hz to drive mechanical watches used at...
Originally, this circuit is from an English magazine, but I found it in Argentina's Radio Chassis...