cryotron (krĪˈōtrŏnˌ) [key], magnetically controlled electronic switching device that operates at extremely low temperatures; it is designed to supplant, in part, the transistor in special electronic equipment (e.g., the computer). One type of cryotron consists of a straight wire (the gate) around which a wire coil (the control coil) is wound. Kept at temperatures near absolute zero, both wires become superconductors (see low-temperature physics; superconductivity), but when current is passed through the coil, a magnetic field is induced that causes the gate to lose its superconductivity, thus switching off the current through it. Another type of cryotron uses conducting films in place of the wires to increase the switching speed. The cryotron is so minute that many of these devices can be packed into a very small area, thereby greatly increasing the degree of control.