Activation shield (CB6947E)

Found in an 80's Elektor, this circuit can control loads up to 750 mA with the BD139 and 100 mA with the used transistor.

Metronome (CB18215E)
This simple metronome, from 1985 documentation uses only transistors and has two settings. For...
Limiting Amplifier (CB21763E)
This circuit is suitable for modulating AM transmitters. The circuit is from a 1977 radio amateur...
High Voltage Pulser (CB6253E)
This flasher was found in an old Hands On, but uses common components. The optocoupler can be...