This third-order filter was found in a 1975 publication. The circuit must be powered by a symmetrical source. The components can be changed for operation on other frequencies.
This circuit is from American documentation from the 70s. Transistors are not common today, but...
Found in old documentation, this simple test checks both the polarity and the existence of voltage...
This circuit is from a 1987 American publication called Electronics Handbook. The circuit can be...