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 filter was obtained from a Linear Technology manual from the 1990s. The power supply must be...
Found in a 90s Popular Electronics, this circuit is intended for amplifying analog video signals....
Based on a 555, this 80's American documentation circuit detects the voltage of a battery and can then...