This circuit is from the 1983 Intersil Databook. The display is plasma and must be excited by a high voltage circuit. The components used in this configuration are not common today.
This very simple oscillator, with only one transistor, was found in a Japanese magazine in 1967....
This simple bridge circuit can be used for impedance or resistance measurement using a high...
This circuit has the intensity of the signals controlled by the light that falls on the sensor....