This circuit was obtained from the February 1992 Radio Electronics magazine. In it, a bar of 4 LEDs flashes continuously at a speed given by C1 and the setting of R3.
This circuit was found in a 90's espionage publication and serves for analog lines. The circuit is...
This circuit is used in short wave receivers that do not have the BFO (Beat Frequency Oscillator) for...
Found in Popular Electronics from the 1980s, this circuit shows how to drive two charges...