Door buzzer or alarm (CB20492E)

This solar powered circuit was found in a 1991 documentation. The transistor is a general purpose NPN.

Code Practice Oscillator (CB940E)
This circuit uses one of the first comercial transistor and is from a 1958’s magazine. Tone...
Gain 50 Current Sensor (CB5388E)
We found this simple gain-50 current sensing circuit in a 2005 Linear Technology publication. The circuit...
800 W dimmer (CB5294E)
This soft starter dimmer was found in a 1980s documentation. We can implement it with current...