This automatic brightness control that uses an LDR as a sensor, was found in American documentation from the 1980s. Resistors in series with LEDs depend on the desired current.
This 1-transistor circuit appeared in a February 1962 Radio Electronics. The coils for the...
This recyclable automatic timer was found in Radio Electronics magazine from July 1960. The...
This transistor tester was found in a publication by Gernsback from 1960. The circuit can be used...