U
 
 UCD
 
      See uniform call distributor.
 
 UCSD-p
 
      University of California at San Diego operating system.
 
 UDK
 
      User Defined Keys.
 
 UDLC
 
      Universal Data Link Control. Unisys' bit-oriented communications
      standard.
 
 UDP
 
      User Datagram Protocol; the TCP/IP transaction protocol, used for
      such applications as remote network management and name service
      access, that allows users to assign a name to a physical or
      numbered address.
 
 UDP
 
      See user datagram protocol.
 
 UDP/IP
 
      Universal datagram protocol/Internet protocol.
 
 UHF
 
      See ultra high frequency.
 
 UI
 
      UNIX International.
 
 UIL
 
      User Interface Language (Digital Equipment).
 
 UIOC
 
      Universal Input/Output Controller.
 
 ultra hi-res
 
      Ultra high resolution. Generally used to describe the scientific
      and medical imaging displays which have higher than 1280 x 1600
      resolution.
 
 ultra high frequency (UHF)
 
      Radio frequencies in the range of 300 to 3,000 megacycles.
 
 ULTRIX system
 
      Digital Equipment's enhanced native-mode UNIX operating system.
 
 unattended operation
 
      Automatic features of a station's operation that allow the
      transmission and reception of messages with no human operators.
 
 unbundled
 
      Various elements of a system, including services, equipment,
      software, and training are sold separately.
 
 unbundled rates
 
      Rates in which the various rate elements that comprise the service
      are separately stated, thereby enabling the identification of the
      charge for each component of the service.
 
 uncoated paper
 
      Paper stock that has not been treated with a layering or
      calendaring process to give it a glossy sheen.
 
 UNCOL
 
      Universal Computer Oriented Language.
 
 underlap
 
      In facsimile, a defect that occurs when the width of the scanning
      line is less than the scanning pitch.
 
 underscan
 
      The part of an image that falls inside the borders of the display
      screen, (the part that can be seen).
 
 underscore
 
      Typesetting with a horizontal line under it. Used for emphasis.
 
 undetected error rate
 
      See residual error rate.
 
 UNI
 
      User-Network Interface, an ATM standard.
 
 UNIBUS
 
      A single, high-speed bus structure shared by the processor, memory,
      and peripherals.
 
 UNICOMP
 
      Universal Compiler FORTRAN Compatible.
 
 uniform call distributor (UCD)
 
      A device located at the telephone office or in a PBX that
      distributes incoming calls evenly among individuals.
 
 uniform numbering plan
 
      Seven-digit number assigned to each telephone station in a network
      that permits calls to be routed to distant phones from any network
      telephone without any differences in the dialed number.
 
 uniform service order code (USOC)
 
      The information in coded form for billing purposes by the local
      telephone company pertaining to information on service orders and
      service equipment records.
 
 uniform-spectrum random noise
 
      See white noise.
 
 uninterruptible power supply (UPS)
 
      Typically, an auxiliary battery backup which supplies continuous
      power in the event of a power loss.
 
 unit call
 
      One hundred calls per seconds (CCS); used as a traffic unit.
 
 unit spacing
 
      Same as fixed spacing.
 
 universal access number
 
      A single number which, when dialed from anywhere in the country,
      can reach customer sites in various parts of the country. Calls
      from subscribers on exchanges in predetermined areas can be routed
      to other installations, within certain restrictions, for the area
      in question by the customer having the facility.
 
 UNIX
 
      1. AT&T operating system. 2. Bell Laboratories' multiuser operating
      system.
 
 unjustified
 
      Typesetting in which neither side aligns, (both sides are ragged).
 
 unmirrored server
 
      A server that uses one disk drive and one disk channel that
      includes a controller, power supply, and interface cabling.
 
 unshielded twisted-pair (UTP) wire
 
      Twisted-pair cabling without a protective covering.
 
 UPC
 
      Universal Product Code. A standard machine-readable bar code,
      applied to retail products for inventory and pricing management
      purposes.
 
 uplink
 
      The earth-to-satellite transmission channel.
 
 upload
 
      Transferring file(s) from a local client to a remote host computer.
 
 UPS
 
      Pronounced UPs. See uninterrupted power supply.
 
 URL
 
      Uniform resource locator, an address on the Web.
 
 usage duration monitor
 
      The system is alerted to decreases in trunk call durations.
 
 USASCII
 
      See American Standard Code for Information Interchange (ASCII).
 
 USASI
 
      USA Standards Institute.
 
 USENET
 
      A collection of separate bulletin boards, called newsgroups that
      provides user news and e-mail.
 
 user datagram protocol (UDP)
 
      A lower-overhead alternative to TCP. UDP does not verify data
      integrity or sequence packets.
 
 USERID
 
      User Identification.
 
 USITA
 
      United States Independent Telephone Association.
 
 USOC
 
      See uniform service order code.
 
 UT
 
      User Terminal.
 
 UTA
 
      Utility Communication Architecture.
 
 UTP
 
      See unshielded twisted pair wire.
 
 UUCP
 
      UNIX-to-UNIX copy program, a program that enables computers to
      connect to the Internet on an as-need basis.
 
 UUdecode
 
      UNIX-to-UNIX decode allows binary files that have been uuencoded
      into ASCII text files to be translated back into binary files.
 
 UUencode
 
      UNIX-to-UNIX encode allows binary files to be translated into pure
      ASCII text files, permitting them to be transmitted as E-mail via
      SMTP.