Two-tone solar buzzer (CB20493E)

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

12 V to 10 A power supply (CB1219E)
This power supply can provide 10 A currents. Its regulation is made by 7812 integrated circuit. The...
Brake and direction indicator (CB7118E)
This circuit was suggested by Popular Electronics from the 90s. The circuit is quite simple using...
Adapter for 4-track oscilloscope (CB7062E)
Found in a Popular Electronics from the 90s, this circuit transforms an ordinary oscilloscope into a...