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.

1,000 V Voltage Source (CB522E)
This circuit can source up to 1,000 V from a 9 V battery. Output current is very low, some...
Transmitter Detector (CB26100E)
This circuit detects the presence of strong signals from spy transmitters, enabling their...
MW Receiver powered by a Galvano Telluric (CB11144E)
This circuit of a publication from the 70's uses a different type of power that we had already...