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    The user application layer of the open system interconnection (OSI) model.

See uniform call distributor (UCD)

See universal data link control (UDLC)

See User Datagram Protocol (UDP)

See ultrahigh frequency (UHF)

UIO module
See universal input output (UIO module)

IBM's product that supports both Ultimotion & INDEO video.

IBM's video compression algorithm. Although IBM supports INDEO in their OS/2 & Windows systems, IBM feels several OS/2 vertical applications are adequately served by the Ultimotion algorithm. Ultimotion does not offer software scalable playback or single step compression.

ultrahigh frequency (UHF)
The band of frequencies between 300 MHz and 3 GHz

umbrella prices
Refers to regulated prices for services (e.g., long distance) that are offered by telephone companies at levels high enough to allow competitors to enter the market uneconomically and charge lower prices. (See uneconomic entry.)

unattended operation
Automatic features of a station's operation that allow the transmission
and reception of messages with no human operators.

1) A class of product that allows the local exchange carrier (LEC) to
charge the customer for all call attempts regardless of whether the
call was successfully completed. These customers usually use private
branding and pass the costs to the end user. No commission is paid on
unbundled calls. 2) Various elements of a system, including services,
equipment, software, and training are sold separately.

unbundled rates
The rate elements that comprise a service are separately stated,
enabling the identification of the charge for each component of the

In order to open all telecommunications markets simultaneously, local
telephone companies must offer long-distance companies and competitive
access providers access to their "essential" network facilities through
a process called unbundling. Essential facilities are defined by the
California Public Utilities Commission as "services or functions which
are only available from one provider (i.e., no other reasonable
alternatives exist)" and include capabilities that competitors require
in order to serve their customers.

undetected error rate
See residual error rate

uneconomic entry
Refers to a situation in which an industry's long-term unit costs of
producing a good or service increase because entry from competitors
occurs. For example, when the prices of services are artificially
maintained above their costs to cross-subsidize local service, an
entrant could undercut the existing price, yet have higher unit costs
than the telephone companies. This would result in an increase in
industry unit costs.

user-to-network interface

A single, high-speed bus structure shared by the processor, memory, and

uniform call distributor (UCD)
A device located at the telephone office or in a wireless private
automatic branch exchange (PABX) that distributes incoming calls evenly
among individuals.

uniform numbering plan
A system of 7-digit numbers assigned to each telephone station in a
network permitting calls to distant phones from any network telephone
without any differences in the dialed number.

uniform resource locator (URL)
The standard format for the address of any resource on the Internet
that is part of the World Wide Web. For example,

uniform service order code (USOC)
A set of codes developed by the Bell System and used by local telephone
companies as a standard means of identifying service or equipment for
billing purposes.

uniform spectrum random noise
See white noise

uninterruptible power supply (UPS)
An auxiliary battery backup that supplies continuous power in the event
of a power loss.

A signal stream in which all one bits are the same voltage polarity.
Zero bits normally are zero volts.

Unipolar return-to-zero
A unipolar signal with a 50 percent duty cycle for each pulse.

unit 1)
A manageable piece of related code, such as one form. 2) An entity such
as beds, rooms, or inmates per pay phone used to base estimated usage

unit call
A traffic unit of one hundred calls per seconds (CCS).

universal access number
A single number that, 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.

universal data link control (UDLC)
The Unisys bit-oriented communications standard.

universal input output (UIO module)
An STDX module that serves to connect to various input/output (I/O)

universal name space
The set of all unique object identifiers in a domain, network,
enterprise, and so forth. Object naming standards and methods for
locating and sending messages to mobile objects are required in
large-scale, object-oriented, distributed-computing systems.

universal night answer
A private branch exchange (PBX) feature that permits any station dial a
single digit to answer an incoming trunk call when no attendant is

Universal serial bus (USB)
A specification for a new high-speed (12Mbps) serial port for PCs.
Initial USB devices will include modems, telephones, monitors, and
keyboards. USB supports up to 127 devices.

universal service
As defined by the National Communications Act of 1934, unicersal
service supports policymakers' efforts "... to make available os far as
possible, to all the people of the United States a rapid, efficient,
nationwide ... wire and radio communication service with adequate
facilities at reasonable charge..." Today, a very large number of
telephone customers receive their service through a subsidized system
that balances the cost of providing service through various means. Due
to the accelerating pace of technology and competition, policy makers
and telecommunications providers are re-evaluating the concept of
universal service.

Accessibility to telephone services at an affordable price by anyone
who wishes to have it.

The Bell Laboratories multiuser operating system. Unix is designed to
be used by many people at the same time and has transmission control
protocol/Internet protocol (TCP/IP) built in. It is the most common
operating system for servers on the Internet. The acronym stands for
Uniplexed Information and Computer Systems.

Unix-to-Unix copy (UUCP)
1) Originally a Unix program that permitted file transfer between two
Unix-based PCs through a dial-up connection. 2) A Unix networking
protocol or any network using that protocol.

unmirrored server
A server that uses one disk drive and one disk channel that includes a
controller, power supply, and interface cabling.

Insufficient information available to determine the correct rate.

unshielded twisted-pair (UTP)
Twisted-pair cabling without a protective covering. For example,
datagrade twisted-pair (DTP) and distributed inside wire (DIW). See
twisted-pair cable.
twisted-pair cable (STP and TSP)

Occurs when the telephone count in an exchange (i.e., the number of
phones that can be reached toll-free, times a weighting factor)
outgrows its current rate group and moves it to the next highest local
rate group. Each rate group has a minimum and a maximum number of
permitted telephone lines which determines the basic local rate
customers pay for telephone service.

The user program layer of the open system interconnection (OSI) model.

The earth-to-satellite transmission channel.

To send a program from your computer to a BBS.

See uninterruptible power supply.
uninterruptible power supply (UPS)

The relative position of two stations in a ring. A station is upstream
of its neighbor if it receives the token before its neighbor receives
the token.

See uniform resource locator.
uniform resource locator (URL)

US half circuit
A logical circuit between the US International Test and Maintenance
Center (ITMC) and the theoretical midpoint (TMP).

usage duration monitor
A device that alerts the system of decreases in trunk call durations.

usage sensitive pricing (USP)
Charges for service(s) that are based on usage.

See American Standard Code for Information Interchange (ASCII)

See Universal serial bus (USB)

use case
See scenario

See User Network (Usenet)

user class of service
A category of data transmission provided in a network in which the data
signaling rate and terminal operating mode are standardized.

User Datagram Protocol (UDP)
The IP standard protocol that allows an application program on one
machine to send a datagram to an application program on another
machine. UDP uses the Internet IP to deliver datagrams.

user ID
A unique identifier associated with a user name on a server system.

User Network (Usenet)
Usenet is an extremely popular Internet tool for spreading and sharing
ideas and information among cooperating computer hosts. The users
communicate through text in newsgroups, which is a forum for discussing
particular interests or topics. Usenet news can be accessed through a
WWW (World Wide Web) browser or through all networks which can exchange
electronic mail either directly or through mail gateways.

user-defined macro
A REACT 2000 option allowing a tester to record the steps taken to test
a circuit, and to later play back those steps automatically to test
another circuit of the same type.

User-to-Network Interface (UNI)
The reference point where the protocols for compatibility between
customer premises equipment (CPE) and a carrier network must be
defined. A UNI specification defines in detail the Layer 1 and Layer 2
and perhaps Layer 3 protocols which are required for CPE and carrier
equipment to interoperate.

See uniform service order code (USOC)

See usage sensitive pricing (USP)

utility service
A service for which there is little or no choice of suppliers.

See unshielded twisted-pair (UTP)

See Unix-to-Unix copy (UUCP)

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Since November 20, 1999

Created by Jim Needham

İVector Graphics 1995

Revised: February 16, 2011
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