This commercial receiver from the year 1958 uses two AA cells as Power supply. The circuit is intend to receive MW station and the transistors are germanium types not easy to find today.
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...