This circuit, found in a 1958 magazine, is for reference only, since the components are not easy to find today. The transistors are germanium types and power supply is made by common cells.
This simple 555 biofeedback circuit was found in the December 1983 issue of Radio Electronics...
Found in a 1969 EDN, this high current circuit, not indicated in the documentation, uses...
This tester for common unijunction transistors is nothing more than a low frequency oscillator...