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.
We found this circuit in an English publication from the 90's. The circuit emits a sound by the...
Found in a Popular Electronics from the 90s, this circuit triggers an indicator when these lights...
This RCA circuit has current limitation. The circuit is from an ancient American documentation making...