A lever or a control button that utilizes superconductivity: A cryotron is a cryogenic device that uses the principle that a varying magnetic field can cause the resistance of a superconducting element to change rapidly between its high normal and low superconductive values: used as a switch and as a computer-memory element.

A cryotron is a superconductive device in which current in one or more input circuits magnetically controls the superconducting-to-normal transition in one or more output circuits.