Found in Popular Electronics from the 90s, this circuit uses a reed switch on the rails as a sensor. Instead of lamps, in a modern version, LEDs can be used.
In the figure we have a circuit that allows us to obtain a variable voltage of approximately 0.5 to 25 V...
This interesting circuit, found in a 1997 documentation, allows you to view the characteristic curves of...
This circuit generates a tone whose frequency is set at VR1. The signal is reproduced in a...