Found in a European magazine from the 90s, this circuit emits beeps that are several seconds apart to indicate that a device is on. The transducer is a ceramic or crystal capsule.
This two-transistor amplifier can be used as power stage for intercom, experimental receivers,...
This proximity relay circuit was found in the July 1990 Radio Electronics magazine. The supply...
With an ultra-low consumption, this circuit can be powered by solar cells. The circuit is from a...