Micro metronome (CB20743E)

This simple CMOS metronome circuit can be mounted in a small box, providing both sound and light sources.

Audio Frequency Meter (CB20477E)
Found in a Popular Electronics from 1992, this circuit uses a PLL567 in an audio meter bridge that...
Two-tone solar buzzer (CB20493E)
This circuit was found in a 1991 publication. The transistor can be a general-purpose type....
Zirconium Arc Projector Power Supply (CB24201E)
This is a different circuit for a component from the past, the zirconium arc lamp used in...