Two-tone solar buzzer (CB20493E)

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

Triangle to sinusoidal converter XR2208 (CB24549E)
This circuit for frequencies up to a few tens of megahertz was found in the April 1978 issue of...
Negative Voltage Generator (CB16629E)
This is another possible version of a negative voltage generator using a 555 integrated circuit. The...
Voltage controlled dimmer (CB22140E)
This Dimmer circuit for incandescent lamps was found in an English documentation. The input...