This circuit was found in ancient American documentation. It provides a 70 Vpp signal at frequencies up to 100 kHz. Observe the high supply voltage.
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...