Found in old documentation, this circuit uses a double gate MOSFET. The operating frequencies depend on the coil, and the indicator is a microammeter.
This circuit encodes the two channel signals from an amplifier for a multiplex-stereo...
This radio for the medium wave band was found in an old American documentation. The transistors are made...
This lock-up alarm circuit was found in a 1990s Radio Electronics magazine. The sensors are...