This circuit is from the 1983 Intersil Databook. The circuit has an A / D converter for display of 4 and a half digits being powered by a voltage of 9 V.
This transistorized circuit is powered by a voltage of 6 to 12 V providing high voltage for a neon...
This circuit is from an Electronics World of 1968. The transistors are of the time and the power...
This circuit is from a 1972 German magazine Funkshau. The circuit can use BC548 transistors...