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
Uniform Call Distributor (UCD) - Device located at the telephone office or with a PABX; distributed incoming calls evenly among stations or agents.
Uninterruptible Power Supply (UPS) - Battery back up system; in the event of a power failure, the UPS converts DC battery power to AC power to run the system.
Universal Digital Carrier (UDC) - Aka Digital Loop Carrier (DLC) - where two analog telephone lines are placed onto one digital copper pair. Used where a customer requests a second line, but no additional copper pairs are available. Central office routes the two lines to a UDC trunk which is then connected to the copper pair that carries the digital transmission to the customer's premises. UDC adapter is connected at the demarcation point, which converts the UDC transmission into 2 analog lines.
Universal Resource Locator (URL) - An internet address, like http://www.pvcsolutions.com. The http:// requests a web page using HTTP, and pvcsolutions.com is the domain name on the World Wide Web (www).
Universal Service Order Code (USOC) - Defines equipment and services within RBOC's. Different RBOC's have different meanings for each code for services, but the codes for equipment has stayed the same since before 1984.
Unspecified Bit Rate (UBR) - A quality of service defined by the ATM Networks/ATM Forum, allowing any amount of data up to a set maximum to be sent across a network; non-time sensitive data that could be retransmitted without significant inconvenience. Does not guarantee freedom from delay or cell loss.
Upstream - bandwidth or information flow toward a service provider, away from the customer, in asymmetrical broadband transmissions.
Usage-Sensitive Pricing - Charge for service based on the amount of use.
Usage-Sensitive Service - Pay-for-what-you-use method of charging for calls.
User Datagram Protocol (UDP) - Connectionless transport-layer protocol; part of the TCP/IP protocol stack. Exchanges datagrams/packets without guaranteed delivery or acknowledgments - error processing and retransmission is handled by other protocols. Sometimes used in place of TCP where transaction-based application programs communicate; normally carries non-critical network information.
User Network Interface - (1) ATM Forum specification; interoperability standard for interface between ATM based routers or switches in private networks, and ATM switches in public carrier networks. A physical layer interface that provides physical layer services to an NNI. (2) Aka cable voice port or voice port; in cable TV networks, a devoice that modulates/demodulates the DS0 voice upstream/downstream channels, located at the telephone subscribers premises - sent by the Host Digital Terminal (HDT) located at the cable TV head end, providing connection to the customer's telephone wiring.
Value-Added Network (VAN) - (1) Data transmission network that routes messages according to available paths. Assures that messages are received as sent; provides user security, high-speed transmission and conferencing among terminals. (2) Public data communications network that provides basic transmission facilities (generally leased by the VAN vendor from an interexchange carrier) plus additional enhanced services such as computerized switching, temporary data storage, error detection and correction, electronic mail service and packet switching.
Variable Bit Rate (VBR) - A quality of service, for ATM networks, with two subcategories. First is Variable Bit Rate - Real Time (VBR-RT) - for timing sensitive connections such as video or voice. Second is Variable Bit Rate - NonReal Time (VBR-NRT_ - used for bursty or other non-time-sensitive transmissions. Both types guarantee minimum delay and cell loss.
Virtual Circuit - (1) Connection between two points in a data network that use different circuits during a transmission but behaves as a dedicated path. (2) Route for packets between a user's terminal and host computer. Circuit is virtual because it appears to the user to be a direct, dedicated circuit between him and the destination.
Voice Grade - (1) Access line suitable for voice, low-speed data, facsimile or telegraph service. (2) Line that generally has a frequency range of about 300 to 3000 Hz.
Virtual Private Network (VPN) - Provides the functions and features of private networks without the need for dedicated private lines between corporate sites. Sites connect to the network provider's network rather than directly to another corporate location.
Voice Over Frame Relay - Way of transporting time sensitive data (like digital voice over frame relay connections). Accomplished by routing voice through a Digital Link Connection Identifier (DLCI) with appropriate classes of service on end router or switch.
Voice over IP (VoIP) - Connecting voice conversations over controlled IP environments (like private networks such as frame realy and ATM).
WATS access line (WAL) - Line class provided from an equal access end office; provides the same service and features as a normal business line (unless mixed interstate and intra state usage is prohibited by the states regulatory body), but incurs different access charges.
Wide Area Telecommunications Servcie (WATS) - Special direct distance dialing (DDD) toll service whereby a subscriber installs a dedicated line arranged for either inward or outward calls (but not both) between the customer's premises and a specific geographical location. Monthly charges are based on the size of the area in which the calls are placed, not on number or length of calls.
Wink Start Signal - Aka Hookflash - sent by PBX systems to central office switches, signaling a request for dial tone or other services.
Wire Center - Geographical service area for a telephone company central office, serving the area that the outside plant (i.e. telephone wires) reaches to.
Wire Pair - Two wires, twisted together.
Wireline Carrier - Local telephone company. FCC regulations restrict providers of cellular telephone service in any given market to one wireline carrier and one non-wireline carrier (any carrier other than the local telephone company).
XC - Cross Connect
x Digital Subscriber Loop (xDSL) - Term that collectively refers to ADSL, HDSL, IDSL, SDSL, and VDSL.