This circuit divides the frequency of a 2 kHz signal by 2. The circuit was found in Philips documentation from 1964. Modern transistors can be used for higher frequencies.
Using SCRs, this circuit from a 1967 General Electric manual allows full wave load control with SCRs....
This interesting circuit from a publication from the 1970s, measures the intensity of the sound...
This simple NPN and PNP transistor tester configuration can use the low current range of a common...