This circuit is from a 1947 Radio Electronics. The 4-tube circuit is battery powered and uses a crystal phone.
This simple circuit with sensors formed by bars or separate screens triggers in the presence of...
This simple circuit presents a voltage gain of about 1,500. The input impedance is high and the...
This circuit came out in a Frances Toute LÉlectronique magazine from July 1978, but can still be...