Found in a 1924 book by Gernsback, this circuit uses a double variable capacitor, a component not very common at the time. Listening was done on a loudspeaker at the time.
We found this circuit in a 2002 documentation. It still uses old type plugs, but it can be adapted to...
This circuit was proposed by a 1965 Electronic Design. Its purpose is to widen the line transients...
The circuit shown can measure currents less than 1 uA and is powered by two 1.5 V batteries in a...