This 1N4742A Zener diode is another form of diode which comes in Through-hole package. Zener diode will mostly be used in a protection circuit or in a crude voltage regulator circuit. Either way, it very important to remember that a Zener diode should always be used along with a Zener resistor. The 1N4742A 12V Zener Diode has a nominal voltage of 12V and like other types of Zener diodes, it can be used as a reference element in voltage regulation, and it can also be used in switching applications and clipper circuits.