This charger for small batteries was obtained from the 1982 Radio Experimenter Handbook. The circuit is low current.
This small transmitter with 2 transistors can reach several hundred meters using a 30 to 70 cm...
This circuit was found in a Modern Electronics from 1990. It activates an old electromechanical pulse counter,...
Although the integrated used originally is uncommon today, more modern operating equivalents can...