The circuit presented was found in the Linear Applications Handbook of the National Semiconductor of 1994. It is based on a DAC1020 and operational not common today.
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...