This circuit is from a 1924 book by Gernsback. The receiver uses two tubes and listens to headphones. Power is supplied by battery with the indicated voltages.
This simple injector circuit can actually be powered by voltages from 3 to 9 V. The frequency is...
This simple timer can be used in many applications such as egg timer. The LED glows up when S1 is...
This circuit locks after a short touch on the sensor. The circuit can be powered by voltages from 5...