This circuit was found in a 1945 publication. The circuit was stated to be part of a walk talkie. Note that, as it is a portable assembly, it was powered by batteries. The jack was for microphone insertion.
This circuit is from a 1995 Electronics Now. It generates a 1 kHz sinusoidal signal. See in the...
Found in a publication by Gernsback from 1960, this circuit uses germanium transistors of the time...
This circuit is based entirely on SCRs. The circuit is from an American 80's documentation; and the PUTs...