SG Chapter 11

V.90 standard

A 56,000-bps dial-up modem standard approved by a standards-making organization rather than a single company; it is slightly incompatible with both x2 and K56flex.

variable bit rate (VBR)

A class of service offered by ATM that is similar to frame relay service. VBR is used for real-time (or time dependent) applications, such as sending compressed interactive video, and non-real-time (non-time-dependent) applications, such as sending e-mail with large, multimedia attachments.

available bit rate (ABR)

A class of service supported by Asynchronous Transfer Mode that is used for traffic that may experience bursts of data (called "bursty" traffic) and whose bandwidth range is roughly known, such as the traffic found in a corporation's collection of leased lines.

frame relay

A commercially available packet switched network that was designed for transmitting data over fixed lines (as opposed to dial-up lines).

cable modem

A communications device that allows high-speed access to wide area networks, such as the Internet, via a cable television connection.

fax-back

A computer-telephony integration (CTI) application in which a user can dial in to a fax server, retrieve a fax by keying in a number, and send that fax anywhere.

asymmetric connection

A connection in which data flows in one direction at a faster transmission rate than the data flowing in the opposite direction; for example, there are numerous systems that have a faster downstream connection (such as from the Internet) and a slower upstream connection.

Modified Final Judgment

A court ruling in 1984 that required the divestiture, or breakup, of AT&T.

class of service

A definition of a type of traffic and the underlying technology that will support that type of traffic. Commonly found in Asynchronous Transfer Mode systems.

permanent virtual circuit (PVC)

A fixed connection between two endpoints in a frame relay network. Unlike a telephone circuit, which is a physical circuit, a PVC is created with software routing tables, thus making it a virtual circuit.

DSL Lite

A form of consumer DSL that has lower transmission speeds and thus lower consumer costs.

rate-adaptive DSL (RADSL)

A form of digital subscriber line in which the transfer rate can vary depending on noise levels within the telephone line's local loop.

splitterless DSL

A form of digital subscriber line in which there is no POTS signal accompanying the DSL signal, thus there is no need for a splitter.

very high data rate DSL2(VDSL2)

A form of digital subscriber line that is very fast (between 51 and 55 Mbps) over very short distances (less than 300 meters).

local access transport area (LATA)

A geographic area, such as a large metropolitan area or part of a large state. Telephone calls that remain within a LATA are usually considered local telephone calls, while telephone calls that travel from one LATA to another are considered long-distance telephone calls.

Asynchronous Transfer Mode (ATM)

A high-speed, packet-switched service, similar to frame relay, that supports various classes of service.

private branch exchange (PBX)

A large computerized telephone switch that sits in a telephone room on the company property.

private lines

A leased telephone line that requires no dialing.

service level agreement (SLA)

A legally binding written document that can include service parameters offered in a service set up between a communications provider and its customer.

incumbent local exchange carriers (ILECs)

A local telephone company that existed before the Telecommunications Act of 1996.

Telecommunications Act of 1996

A major event in the history of the telecommunications industry that, among other things, opened the door for businesses other than local telephone companies to offer a local telephone service.

customized menuing systems

A menu system that can be created and/or changed dynamically according to a user's profile or needs.

competitive local exchange carriers (CLECs)

A new provider of local telephone services (the creation of CLECs was initiated by the Telecommunications Act of 1996).

asymmetric digital subscriber line (ADSL)

A popular form of digital subscriber line that transmits the downstream data at a faster rate than the upstream data.

layer 2 protocol

A protocol that operates at the second layer, or data link layer, of the OSI seven-layer model.

burst rate

A rate agreed upon between a customer and a frame relay provider; this agreement allows the customer to exceed the committed information rate by a fixed amount for brief moments of time.

Centrex (central office exchange service)

A service from local telephone companies through which up-to-date telephone facilities at the telephone company's central (local) office are offered to business users so that they do not need to purchase their own facilities.

integrated voice recognition and response

A system in which a user calling into a company telephone system provides some form of data by speaking into the telephone, and a database query is performed using this spoken information.

interactive voice response

A system that enables a company to user a customer's telephone number to extract the customer's records from a corporate database when that customer calls the company.

call filtering

A technology in which users can specify which telephone numbers are allowed to get through. All other calls will be routed to an attendant or voice mailbox.

digital subscriber line (DSL)

A technology that allows existing twisted pair telephone lines to transmit multimedia materials and high-speed data.

Trunk

A telephone connection used by telephone companies that carries multiple telephone signals, is usually digital and high speed, and is not associated with a particular telephone number.

third-party call control

A telephone feature that allows users to control a call (for example, set up a conference call) without being a part of the call.

symmetric connection

A type of connection in which the transfer speeds in both directions are equivalent.

Cells

An area within a cell phone network that contains a cell tower; all mobile users connect to that cell tower.

V.92

An improvement of the V.90 standard that provides a higher upstream data transfer rate and also provides a call waiting service, in which a user's data connection is put on hold when someone calls the user's telephone number.

PBX graphic user interface

An interface in which different icons on a computer screen represent common PBX functions such as call hold, call transfer, and call conferencing, making the system easier for operators to use.

central office (CO)

Contains the equipment that generates a dial tone, interprets the telephone number dialed, checks for special services, and connects the incoming call to the next point.

tie lines

Leased telephone lines that require no dialing.

computer-telephony integration (CTI)

New telephone services and systems that combine more traditional voice networks with modern computer networks.

network-network interface

One type of connection in Asynchronous Transfer Mode (ATM); a network-network interface is created by a network and used to transfer management and routing signals.

user-network interface

The connection between a user and the network in Asynchronous Transfer Mode (ATM).

text-to-speech and speech-to-text conversion

Telephone systems that can digitize human speech and store it as a text file, and take a text file and convert it to human speech.

plain old telephone service (POTS)

The basic telephone system.

unified communications

The convergence of multiple forms of communications such as messaging, telephony, and video conferencing into a consumer-friendly, unified interface unified messaging.

committed information rate (CIR)

The data transfer rate that is agreed on by both the customer and the carrier in a frame relay network.

xDSL

The generic name for the many forms of digital subscriber line (DSL).

local exchange carriers (LECs)

The name given to local telephone companies after the divestiture of AT&T in 1984.

interexchange carriers (IECs, IXCs)

The name given to long-distance telephone companies after the divestiture of AT&T in 1984.

local loop

The telephone line that leaves your house or business; it consists of either four or eight wires.

virtual path connection(VPC)

Used in Asynchronous Transfer Mode to support a bundle of virtual channel connections(VCCs) that have the same endpoints.

virtual channel connection(VCC)

Used in Asynchronous Transfer Mode; a logical connection that is created over a virtual path connection.

constant bit rate (CBR)

Used in Asynchronous Transfer Mode; an expensive service that is similar to a current telephone system leased line.

unspecified bit rate (UBR)

class of service offered by ATM that is capable of transmitting traffic that may experience bursts of data, but does not make any promise about when the data may be sent.

fax processing

computer-telephony integration (CTI) application in which a fax image that is stored on a LAN server's hard disk can be downloaded over a local area network, converted by a fax card, and sent out to a customer over a trunk line.