This circuit was found in a Radio Electronics from 1970. The coupler with LDR is from that time, but the circuit can be adapted to use modern components and act as a shield.
This circuit was obtained from an English circuit manual. Components are common and LEDs can be 3...
Found in a 90's EDN, this circuit generates signals in the frequency range given by the graph. The...
This circuit can generate signals from 100 kHz to 1 MHz depending on the L1 coil. For the medium...