Two-tone solar buzzer (CB20493E)

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

Battery charger (CB1225E)
This 6 V battery charger was found on a 1987 Hands On Electronics. Rc determines the charging...
1 to 10 mA Constant Current Sourcer (CB1198E )
In the figure we have the way to obtain an adjustable 1 to 10 mAconstant current source. The...
Circuit for Inductors Test (MSB071E)
This circuit is used to test an inductor (coil) allowing the observation of its opration in an R-L...