This circuit is from American documentation from the 1980s. The circuit can make use of any common NPN transistor and the power comes from two small batteries.
This source for 50 W amplifiers per channel was found in 1967 Delco documentation. Transistors are from...
Operated directly from the power grid, this detector was found in an 80's RCA documentation. The sensor is...
This oscillator was obtained in a 1960 transistor manual from Sylvania. The transistors are from...