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.
This circuit was found in a 1992 publication. The circuit uses common components and includes the...
This protection circuit for battery chargers was found in an old Elektor. The relay is according to...
This very low frequency amplifier has a gain of 1,000 and was found in a 1967 documentation. The circuit is...