This circuit is from a 1980's documentation for telecommunications. The circuit is used in SSB and the diodes must be suitable types for the application. The audio input is low impedance.
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...