With this circuit it is possible to vary the resistance by adjusting the mark/space reaction of the 555. The circuit was found in the November 1989 Radio Electronics magazine.
This circuit activates a relay when the conducting bars (probes) are held by a person. The circuit is...
This circuit for the automatic activation of a small lamp (or high brightness LED) was found in...
This circuit was obtained from a 1966 documentation. The transistors are of the time. The circuit...