UL
abb. Underwriters Laboratories

UL fire resistive container classifications

class 125
n. a group of UL classifications for containers that maintain inside temperatures less than 125 degrees Fahrenheit when exposed to a fire of specific temperature and duration. The times and fire temperatures are:
½ hour 1700 degrees F.
1 hour 1700 degrees F.
2 hour 1850 degrees F.
3 hour 1925 degrees F.
4 hour 2000 degrees F.

class 150
n. a group of UL classifications for containers that maintain inside temperatures less than 150 degrees Fahrenheit when exposed to a fire of specific temperature and duration. The times and fire temperatures are:
½ hour 1700 degrees F.
1 hour 1700 degrees F.
2 hour 1850 degrees F.
3 hour 1925 degrees F.
4 hour 2000 degrees F.

class 350
n. a group of UL classifications for containers that maintain inside temperatures less than 350 degrees Fahrenheit when exposed to a fire of specific temperature and duration. The times and fire temperatures are:
½ hour 1700 degrees F.
1 hour 1700 degrees F.
2 hour 1850 degrees F.
3 hour 1925 degrees F.
4 hour 2000 degrees F.

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