A physical interface in an ISDN Basic Rate service which uses a single copper pair.

Universal Asynchronous Receiver/Transmitter

Integrated circuit, attached to the parallel bus of a computer, used for serial communications. The UART translates between serial and parallel signals, provides transmission clocking, and buffers data sent to or from the computer.

Unavailable seconds

Count of seconds for which the monitored entity is unavailable.

Unspecified Bit Rate

A form of ATM transmission in which an information stream is supported on whatever bandwidth is available after other connection types have been satisfied. No congestion control is provided. UBR is commonly used to support information streams originating in LAN switches with ATM uplinks.

Universal Call Model

UniDirectional Link Protocol

Protocol used by inexpensive, receive-only antennas to receive data via satellite.

User Datagram Protocol

A transport-layer protocol that provides connectionless service without packet acknowledgment.

Unidirectional DSL

Is a proposal from a European company. It's a unidirectional version of HDSL.

U Interface - Digital Subscriber Loop

UK Education and Research Networking Association

Transmission direction from the customer toward the central facility.

An International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) standard used for sampling data by means of Pulse Coded Modulation (PCM). U-Law is most commonly used in North America and Japan.

Upper-Layer Protocol

Protocol that operates at a higher layer in the OSI reference model, relative to other layers. ULP is sometimes used to refer to the next-highest protocol (relative to a particular protocol) in a protocol stack.

UMTS Mobile Switching Centre

Universal Mobile Telecommunications System

See 3G

HDLC configuration with one primary station and multiple secondary stations.

User-to-Network Interface

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.

A network in which a router sends packets to one user at a time.

Provides an individual user access, through their mobile terminal, to all the recognised messaging formats including voice mail, facsimile, pager, SMS and email.

Traffic within the excess rate (the difference between the insured rate and maximum rate) for an ATM VCC. This traffic can be dropped by the network if congestion occurs.

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

In broadband networks, the balance between signal loss and signal gain through amplifiers.

A multi-user, multitasking operating system originally developed by AT&T Bell Labs that runs on a wide variety of computer systems.

Unified Network Management Architecture

Set of frequencies used to send data from a subscriber to the headend.

Universal Personal Telecommunications

A relatively advanced IN system.

Universal Resource Locator

A path that takes you directly to the desired site on the World Wide Web; also known as an internet address.

Universal Serial Bus

An external bus that is beginning to replace parallel and serial ports. With a maximum transfer speed of 12 Mbps (megabits per second), USB is designed for low- to mid-speed peripheral devices (such as keyboards, mice, printers, joysticks, and modems) whereas more bandwidth-intensive devices (such as digital video cameras and storage devices) use the IEEE FireWire standard.

Initiated in 1979, one of the oldest and largest cooperative networks, with over 10,000 hosts and a quarter of a million users. Its primary service is a distributed conferencing service called news.

UMTS Subscriber Identity Module

Universal Service Obligation

Unstructured Supplementary Service Data

A method of transmitting messages via the GSM network in an interactive, open session environment. It is GSM based, therefore it works on all existing GSM mobile phones. It is also supported in SIM Application toolkit and WAP.

United States Telephone Association

Universal Test & Operation PHY Interface for ATM

Unshielded Twisted Pair

A cable medium with one or more pairs of twisted insulated copper conductors bound in a single plastic sheath. Now becoming the most common method of bringing telephone and data to the desktop.

Unshielded Twisted Pair Cable

Two paired wires with wire twisted two or more times per inch to help cancel out noise.

Unshielded Twisted Pair of category n

UMTS Terrestrial Radio Access

UMTS Terrestrial Radio Access Network

UNIX-to-UNIX Copy Program

Protocol stack used for point-to-point communication between UNIX systems.

UNIX-to-UNIX Decode

Method of decoding ASCII files that were encoded using uuencode.

UNIX-to-UNIX Encoding

Method of converting binary files to ASCII so that they can be sent over the Internet via e-mail. The name comes from its use by the UNIX operating system's uuencode command.

User-to-User Indentification

A field within ISDN protocol which can provide end-to-end information exchange (telephone number, credit card number, login ID, etc.)

Universal Voice Module

Universal Voice Module-Channelized

Universal Voice Module-Unchannelized

Ultra Wide Band