Linear photometer (CB7366E)

This circuit was found in a 1967 Philips publication. Transistors support equivalents and modern equivalents can be used.

Full wave slave control (CB8156E)
Using SCRs, this circuit from a 1967 General Electric manual allows full wave load control with SCRs....
Sound Strength Meter (CB12930E)
This interesting circuit from a publication from the 1970s, measures the intensity of the sound...
Simple Transistor Tester (CB19460E)
This simple NPN and PNP transistor tester configuration can use the low current range of a common...