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.

Reflex receiver (CB23633E)
This simple 1-transistor reflex receiver was published in Radio Electronics magazine in September 1959....
Voltage Calibrator (CB24703E)
This circuit was found in the June 1982 issue of Radio Electronics magazine. It provides reference...
Optical memory for AC control (CB20694E)
This circuit was found in an American documentation from the 90s. It consists of an optical memory...