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 generates low-frequency sinusoidal signals. The variable capacitor is dual and the...
These circuits were obtained in an Electronics Now from the 90s. The integrated circuits are from...
This circuit for voltages up to about 20 V was found in a 90s Popular Electronics. The LED can be...