This an old commercial receiver found in a year 1958 magazine. The circuit uses some transformer available that timer and the transistors are germanium types. The circuit is intended to receive MW stations.
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...