This battery-powered 3-valve circuit was found in American documentation from 1947; Two batteries are used, one high voltage and one low voltage for the filaments.
This simple injector and signal follower employs a high impedance headset. Transistors can be of...
This well-known siren configuration using complementary transistors is from a 1980s documentation. The...
This vox was found in Hughes documentation from 1968. The circuit uses components from the era. A...