This primitive solar radio was found in a Gernsback publication from 1960. The transistor is made of germanium of the time and the earphone is magnetic with high impedance.
Found in an American documentation from 1968, this circuit uses transistors from the time. The...
This circuit was found in a 1980s Intersil documentation. The integrated circuit used is not...
This simple 3-channel passive mixer can be used with low-intensity signal sources but requires...