This circuit was found in a Motorola documentation from 1968. The circuit makes use of FETs and bipolar of the time and can be applied to modern equivalents.
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...