This simple audio and RF signal tracker was found in a Japanese publication in 1967. The transistors are made of germanium and the headphone is made of crystal.
This circuit for controlling high power in the AC network was found in a Motorola documentation from 1968....
Found in American documentation from the 90's, this circuit consists of a solid state relay with...
This oscillator uses a small transistor amplifier or radio output transformer. We found it in a...