U-Bend Test
A cable test in which the insulation is tested for resistance to corona and ozone

UF
A UL cable type. Thermoplastic underground feeder or branch circuit cable

UHF
Ultrahigh Frequency. The band extending from 300 to 3,00 mHz as designated by the Fedral Communications Commission

UL
Underwriters Laboratories, Inc

UL Listed
A product that has been tested and found to comply with the Underwriters Laboratories' standards

Ultrasonic Cleaning
Immersion cleaning aided by ultrasonic waves which cause microagitation

Ultrasonic Detector
A device that detects ultrasonic noise such as that produced by corona or leaking gas

Ultraviolet
Radiant energy within the wavelength range 10 to 380 nanometers. It is invisible, filtered out by glass, and causes suntan

Unbalanced Line
A transmission line in which voltages on the two conductors are unequal with respect to ground, eg., coaxial cable

Unbalanced-to-Ground
Describing a two-wire circuit, where the impedance-to-ground on one wire is measurably different from that on the other. Compare with Balanced-to-Ground

Undirectional Conductor
See Concentric-Lay Conductor

Undirectional Stranding
A term denoting that in a stranded conductor all layers have the same direction of lay

Unilay
More than one layer of helically laid wires with the direction of lay and legth of lay the same for all layers. See Concentric-Lay Conductor

USE
A UL cable type. Underground service entrance cable, XLP or rubber-insulated, Hypalon or XLP jacketed

UTP
Unshielded Twisted Pair. Two wires, usually twisted around each other to help cancel out any induced noise in balanced circuits. An unshielded twisted pair cable usually contains four pairs of wire in a single cable jacket

USCG
United States Coast Guard