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 is intended to trigger a TTL door or flip-flip from a signal coming from an SCR....
This circuit found in a 1988 documentation, uses a piezoelectric or crystal capsule as a...
This circuit, which can be used as a shield, was found in Radio Electronics from the 90s. The...