(We wish to thank Unicom for their contributions.)
# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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.