This circuit found in a 90s Popular Electronics, triggers a huge array of LEDs from the sounds captured by a microphone, thus generating visual effects.
This circuit was obtained in the manual of the used integrated circuit. Equivalents may be used...
The UVTRON tube is an ultraviolet radiation sensor. In this circuit from Radio Electronics from...
This circuit was suggested by Popular Elecronics from the 90's. The circuit has high input...