Found in the CQ radio amateur magazine, this circuit generates a standard 100 kHz signal. The circuit is from 1965 and can be made with modern equivalent transistors.
This sound effect circuit was obtained from an article in the April 1969 issue of Radio...
Found in a 1990 Electronics Handbook, this circuit causes an LED to flash when the phototransistor receives...
Found in the May 1997 issue of Electronics Now, this circuit produces a variety of sound effects for...