Two-tone solar buzzer (CB20493E)

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

5A Fixed and Adjustable Regulator (CB1233E)
ST Microelectronics has, in its line of low voltage drop linear regulators, the KD1084xx (fixed) and...
Light amplifier (CB7505E)
In fact, this circuit found in a 1960 transistor manual from Sylvania, simply turns on a lamp when...
Gel Battery Charger (CB6053E)
We found this circuit in an 80's Electronic Design. The circuit uses an integrated of the time....