This simple optical alarm circuit was found in the 1991 Electronics Experimenter Handbook. The circuit uses a lamp as the emitter but can use LEDs.
This XTAL oscillator was found in the January 1986 issue of Radio Electronics magazine. Any gate...
This circuit is from a documentation for 1976 radio amateurs. We can implement this circuit with...
This sophisticated filter for audio signals was found in Radio Electronics magazine. The...