This simple indicator circuit was found in a documentation from the 90s. Trimpots can have values between 2k and 10k, a series resistor is recommended to limit the current to the minimum setting.
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...