Two-tone solar buzzer (CB20493E)

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

4 to 20 MHz Oscillator (CB386E)
XTAL from 4 to 20 MHz can be used in this oscillator. The XRF choke can range from 10 to 100 µH...
LM393 Zero Crossing Detector (CB4484E)
This zero crossing detector is of the 1993 Motorola Linear Interface ICs. The source is...
Mini Flasher (CB4416E)
This conventional slow-moving circuit uses incandescent light bulbs, but can be changed to use...