Two-tone solar buzzer (CB20493E)

This circuit was found in a 1991 publication. The transistor can be a general-purpose type.

Who is the fastest Game with SCR (CB3857E)
This well-crafted speed game setup for two competitors was found in a 1998 Poptronics. The circuit...
Mini Electronic Organ (CB926E)
I found this electronic organ in magazine published in 1976 from my vast collection of foreign...
Gain 10 Tone Detector (CB4906E)
This circuit was found in an application note of the LTC1164 from Linear Technology of the 1990s....