UL - Abbreviation for Underwriters Laboratories, a nonprofit independent organization, which operates a listing service for electrical and electronic materials and equipment.

UNF - Abbreviation for ultra high frequency, 300 to 3,000 MHz.

USOC (Uniform Service Ordering Code)* - A term originally used by the telephone company to specify installation of a standard modular jack.

UTP (Unshielded Twisted-Pair)* - A type of twisted-pair wire that has no metalized outer covering, shielding the pairs of wire. The pairs are typically covered with a plastic sheath.

Velocity of Propagation - The speed of an electrical signal down a length of cable compared to speed in free space expressed as a percent. It is the reciprocal of the square root of the dielectric constant of the cable insulation.

VF-45* - A fiber connector using V-groove technology instead of ferrules used in traditional SC fiber-optic connectors. The mechanical connection formed with the V-grooves reduces installation time from approximately 15 minutes to 2 minutes. The connector is tested to ISO-11801, the current TIA-568-A premises cabling standards, and the corresponding component standards. The Fiber Channel Association ASC-x3t11 Technical Committee adopted the design in February 1997 as the new, small-form factor interface for future variants of Fiber Channel.

VHF - Abbreviation for very high frequency, 30 to 300 MHz.

Video Pair Cable - A transmission cable containing low-loss pairs with an impedance of 125 ohms. Used for TV pick ups, closed circuit TV, telephone carrier circuits, etc.

VLAN (Virtual Local Area Network)* - In a switched network, a logical collection of devices, such as workstations and servers with a particular IP subnet address, which are grouped into a broadcast domain. Usually, this domain is software based as opposed to a physical LAN, which is defined entirely by wiring.

Volt - A unit of electromotive force

Voltage Rating - The highest voltage that may be continuously applied to a wire in conformance with standards or specifications.

Voltage Standing Wave Ratio (VSWR) - The ratio of the maximum effective voltage to the minimum effective voltage measured along the length of mismatched radio frequency transmission line.

VW-1 - A flammability rating established by Underwriters Laboratories for wires and cables that pass a specially designed vertical flame test.

Wall Thickness - The thickness of the applied insulation or jacket.

WAN (Wide Area Network)* - A network that covers a larger geographical area such as a state or country.

Watt - The unit of electric power.

Wave Length - The distance, measured in the direction of propagation, of a repetitive electrical pulse or wave form between two successive points the, are characterized by the same phase of vibration.

Wire - A conductor, either bare or insulated.

Workstation* - A terminal station, usually connected to a LAN, providing local processing capability and storage as well as access to other workstations and shared resources.