This circuit was found in a Popular Electronics from the 90's. The transistors are general-purpose types and the loaded load depends on the voltage and must have a maximum current of 100 mA.
Suggested by General Electric in a 1967 documentation, this circuit replaces the Thryraton tubes used at...
This circuit came out in a Popular Electronics from December 1995. It is a double T configuration that...
This circuit can measure capacitances in various ranges using a common analog indicator. The...