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UL listed

adj. listed in a directory as having passed specific Underwriters Laboratories testing

unassociated change key

n. a change key which is not related directly to a particular master key through the use of certain constant cuts

unassociated master key

n. a master key which does not have change keys related to its combination through the use of constant cuts

uncombinated

adj. 1. of or pertaining to a cylinder which is or is to be supplied without keys, tumblers and springs 2. of or pertaining to a lock, cylinder or key in which the combination has not been set

uncontrolled cross keying

n. a condition in which two or more different keys under different higher level keys operate one cylinder by design; e.g., XAA1 operated by AB, AB1. Note: This condition severely limits the security of the cylinder and the maximum expansion of the system, and often leads to key interchange

unibolt

n. a single plate of steel used in place of individual multiple bolts to lock a safe door

unidirectional cylinder

n. a cylinder whose key can turn in only one direction from the key pull position

USB key

n. a hardware key connected to a USB port