Access Charge
A fee charged from subscribers or other telephone companies by a local exchange carrier for the use of its local exchange networks.

Access Services
Access services are specified sets of information transfer capabilities furnished to users at telecom network’s points-of-termination to provide access to network-transport services.

Acoustic Coupler
A device that enables a modem to connect to a voice circuit. A handset adapter is used to receive modem tones through the handset’s mouthpiece, and the earpiece is used to transmit these tones to the modem.

Adapter
A mechanical media termination device designed to align and join fiber-optic connectors. Often referred to as a coupling, bulkhead or interconnect sleeve.

Address Signals
Address Signals convey destination information such as a called 4-digit extension number, central office code, and when required, area code and serving IXC carrier code. These signals may be generated by station equipment, or by a switching system.

Advanced Mobile Phone System
The current analog cellular FM system in North America. It uses 30 kHz channels, and signaling is done through superaudio.

AMPS
Advanced Mobile Phone Service. The analog wireless transmission standard (technology) deployed in the 1980s in the US and Canada. AMPS operates at 800 MHz. Also see N-AMPS (Narrowband AMPS).

AMSS
Automatic Multiple Site Switching. This will allow the mobile radio unit to make a wide area call.

Antenna
A physical device for sending or receiving radio signals. Antennae come in a variety of shapes and sizes. Some wireless phones contain built-in antennae.

Aperture
A cross sectional area of the antenna, which is exposed to the satellite signal.

Application Level Gateway
A firewall system in which service is provided by processes that maintain complete TCP connection state and sequencing. Application level firewalls often readdress traffic, so that the outgoing traffic appears to have originated from the firewall rather than the internal host.

ASIC
Application Specific Integrated Circuits. These are custom designed to handle specific operations; all functionality is cast in hardware.

Asynchronous Mode
A way to send transmissions by starting and stopping transmissions with a code rather than sending transmissions at specific time intervals as in synchronous mode.

ATDM
Asynchronous Time Division Multiplexing

ATM
Asynchronous Transfer Mode. A technology for broadband transmission of high-capacity telecommunications signals. In addition to high-capacity signal transmission, ATM provides considerable flexibility, since the individual subscriber is able to adapt the capacity of a switched connection to current requirements.

Automatic Call Distribution
ACD is a means for efficiently directing and managing large numbers of incoming calls to specific departments/terminals within an organization.

Automatic Call Distributor
The specialized telephone system used in incoming call centers. It is a programmable device that automatically answers, queues and distributes calls to agents, plays delay announcements to callers and provides real-time and historical reports on these activities.

Automatic Number Identification
A service feature in which the directory number or equipment number of a calling station is automatically obtained.

Average Revenue Per User (ARPU)
A primary element of valuation and analysis of wireless companies. It reflects the average amount of revenue generated by each subscriber.

B Channel
In an ISDN system, it is the bearer channel that carries voice or data at 64 kbps in either direction. This is in contrast to the D channel, which is used for control signals and data about the call. Several B channels can be multiplexed into higher-rate H channels.

Backbone
A high-speed line or series of connections that forms a major pathway within a network. The term is relative, as a backbone in a small network will likely be much smaller than many non-backbone lines in a large
network.

Band
In wireless communication, band refers to a frequency or contiguous range of frequencies.

Bandwidth
The width or capacity of a communications channel. Analog bandwidth is measured in Hertz (Hz) or cycles per second. Digital bandwidth is the amount or volume of data that may be sent through a channel, measured in bits per second, without distortion.

Base Station
The central radio transmitter/receiver that maintains communications with a mobile radio telephone with a given range.

Baseband
In networking, a baseband connection is one that uses digital signals, which are sent over wires without modulation; that is, binary values are sent directly as pulses of different voltage levels rather than being superimposed on a carrier signal (as happens with modulated transmissions).

Beacon
A low-power carrier transmitted by a satellite, which supplies the controlling engineers on the ground with a means of monitoring telemetry data, tracking the satellite or conducting propagation experiments. This tracking beacon is usually a horn or omni antenna.

BISDN
Broadband ISDN. A packet switching technique that uses packets of fixed length, resulting in lower processing and higher speeds.

Bit
A single digit number in base-2, in other words, either a 1 or a zero. The smallest unit of computerized data. Bandwidth is usually measured in bits per second.

Blackout
Total loss of utility power.

Blocked Call
A call that cannot be connected immediately because no circuit is available at the time the call arrives, or the ACD is programmed to block calls from entering the queue when the queue backs up beyond a defined threshold.

Bluetooth
An industry-standard for a low power short-range radio link for connecting electronic devices. Devices such as mobile phones, laptop computers and digital cameras equipped with Bluetooth can share data information within a range of about 10 meters. Neither cables nor line-of-sight infrared are needed.

BPS
Bits Per Second. A measurement of how fast data is moved from one place to another. A 28.8 modem can move 28,800 bits per second.

Bridge
A device that connects and passes network segments that use the same communications protocol. Bridges operate on the data link layer (layer 2) of the OSI reference model.

Broadband
A local area network (LAN) residing on coaxial cable capable of transporting multiple data, voice and video channels. Broadband channels have enough bandwidth to carry full motion video, stills, graphics, audio and text (e.g., fiber optics, cable TV, ITFS)

Buffer Box
A device that temporarily stores data, usually between two devices with different data speeds; sends data out at a speed that the slower machine can handle.

Burst Speed
The maximum speed at which a device can operate without interruption, generally only for short periods. This is in contrast to throughput, which indicates the average speed at which a device can operate under ordinary conditions.

C Band
Band of frequencies used for satellite and terrestrial communications. Range of frequencies from 4 to 6 GHz (billion cycles per second) is used by most communications satellites. The 3.7 to 4.2 GHz satellite communication band is used as the downlink frequencies in tandem with the 5.925 to 6,425 GHz band that serves as the uplink.

Call Accounting
Call accounting applications involve using software to track information about individual calls (number dialed, time, length, etc) in order to track usage, recover costs, bill for services, reconcile bills and more. Call accounting applications are generally easy to justify in environments where telephone use is intensive and time is billed.

Call By Call Routing
The process of routing each call to the optimum destination according to real-time conditions.

Call Detail Recording
Data on each call, captured and stored by the ACD. Can include trunk used, time in queue, call duration, agent who handled the call, number dialed (for outgoing calls) and other information.

Call Park
A call park number allows the user to ‘park’ a call at a specified directory number, go to another phone and dial the ‘park’ number to retrieve the call. This is different from ‘Hold’ because the user can retrieve the call from any phone on the same system.

Caller ID Features
Caller ID service is available from most local telephone companies. With a product equipped for caller ID, the service allows consumers to see the name and/or number of the calling party before answering their call.

Call Routing
Call routing solutions are also programmed telephony solutions that automate the delivery of calls to the selected individuals. Calls can be routed based on associated information provided by the telephone system, or on an actual interaction with a caller, using voice processing.

Call Screening
Call screening solutions use CTI technology to filter calls and handle them differently, depending upon who is calling or why. Call screening solutions may involve screen-based telephony, programmed telephony software or a combination of the two.

Carrier Frequency
The rate at which the carrier signal repeats, measured in cycles per second or hertz. The main frequency on which a voice, data or video signal is sent. Microwave and satellite communications transmitters operate in the band from 1 to 14 GHz (a GHz is one billion cycles per second).

Carrier
A company that provides telecommunications circuits. Carriers include both local telephone companies and long distance providers.

Category 5
A performance classification for twisted-pair cables, connectors and systems. Specified to 100 MHz. Suitable for voice and data applications up to 155 Mbps (possibly 1,000 Mbps).

Category 5e
Also called Enhanced Category 5. A performance classification for twisted-pair cables, connectors and systems. Specified to 100 MHz. Suitable for voice and data applications up to 1,000 Mbps.

CCITT X.25
CCITT specification and protocol for public packet-switched networks

CCITT
Consultative Committee on International Telegraph and Telephone. Older international standards body. Now called the ITU, it has been superseded by a new organization, the TSB, which will continue to recommend and publish worldwide communications standards. Also see ITU-TSS

CDPD
Cellular Digital Packet Data. A technology for wireless mobile communications.

Cell
The geographic area encompassing the signal range from one base station (a site containing radio transmitter/receiver and network communication equipment). Wireless transmission networks are comprised of many hexagonal, overlapping cell sites to efficiently use radio spectrum for wireless transmissions. Cells can be anywhere from a few km to 32 km (20) miles in diameter. Also the basis for the term ‘cellular phone’.

Cellular
In wireless communications, cellular refers most basically to the structure of the wireless transmission networks, which are comprised of cells or transmission sites. The term ‘cellular phone’ is used interchangeably to refer to wireless phones.

Cellular Digital Packet Data
Sending digital data over the existing advanced mobile phone system by transmitting dense packets on vacant analog channels.

Centrex
A telephone business service provided by a local phone company from a local central office and provides features directly to each phone at a business without using an on-site PBX.

Channel
A channel is a physical or logical path for a signal transmission. Channel frequencies are specified by respective governments. In telecommunications, a single cable may be able to provide multiple channels. Television signals require a 6 MHz frequency band to carry all the necessary picture detail.

Circuit Switching
A switched circuit is only maintained while the sender and recipient are communicating as opposed to a dedicated circuit which is held open regardless of whether data is being sent or not.

Circuit-switched Gateways
The process of configuring and maintaining an open circuit between two or more gateways so those gateways have the exclusive use of the circuit until the connection is released.

CLEC
Competitive (or certified) local exchange carrier - the Telecommunications Act of 1996 opened the door for smaller companies to compete with the incumbent LECs, such as regional BOCs for local, long distance, international, Internet and entertainment.

Cloning
Cellular cloning occurs when a criminal uses sophisticated equipment to capture a customer’s phone and serial numbers when a call is being made. The criminal can program these numbers into another phone to make illegal calls.

CMTS
Cellular Mobile Telephone System. A cellular mobile radio system interconnected to a local telephone or to the public telephone network.

Coax, Coaxial Cable
Also called coaxial line. A transmission line in which the inner conductor is completely surrounded by an outer conductor (the shield—either a solid metal or braided metal grounded shield), so that the inner and outer conductors are coaxially separated. The line has no external field and it is not affected by external fields.

Co-Location
The ability of multiple satellites to share the same approximate geostationary orbital assignment frequently due to the fact that different frequency bands are used.

Computer Telephony Integration
The software, hardware and programming necessary to integrate computers and telephones so that they can work together seamlessly and intelligently.

Conditional Routing
The capability of the ACD to route calls based on current conditions. It is based on ‘if-then’ programming statements. For example, ‘if the number of calls in agent group 1 exceeds 10 and there are at least 2 available agents in group two then route the calls to group two.’

Connector
A mechanical device used to align and join two fibers together to provide a means for attaching to and decoupling from a transmitter, receiver or another fiber (patch panel).

Control Channel
The RF channel that is used to communicate to all mobiles. This tells the mobiles about the incoming telephone calls, what channel to go to for dispatch and interconnect calls, and other more technical things. It will always be on channel one, two, three or four.

Copper Cables
Assembly of one or more twisted-pair insulated conductors enclosed in a protective sheath, such as polyethylene, aluminum, lead, etc. Commonly used in telephony works.

Correlator
The receiver component that demodulates a spread spectrum signal—a device that measures the similarity of an incoming signal and a stored reference code.

Cramming
The illegal practice of adding charges to consumers’ phone bills for products or services without proper authorization from the customer.

Current Loop
A communications method that transmits data as current flow over relatively long distances and through environments with relatively high noise.

Customer Relationship Management
Where companies use a variety of methods and contact strategies to try to build lasting and profitable relationships, in order to retain the best customers and generate profitable revenue.

D Channel
In an ISDN system, the D channel is the data or signaling channel. The D channel is used for control signals and data about the call. This is in contrast to the B channel, which serves as a bearer for data and voice.

DAMA
Demand-Assigned Multiple Access. In telecommunications, a method for allocating access to communications channels. Idle channels are kept in a pool. When a channel capacity is requested, an idle channel is selected, allocated the requested bandwidth, and assigned to the requesting party. Typically used in a packet-switched environment.

Dark Fiber
A fiber strand without any light flowing through it. With DWP’s dark fiber, customers may attach their choice of voice, data and/or video equipment to the ends of their licensed fibers to ‘light’ the fibers and transmit information between locations.

Data Compression
The process of reducing the size of data parcels to transmit more data in less time. In modems, a bit encoding process that removes redundancy from the scanned page, resulting in fewer bits to transmit.

Data Port
Any PC with RS 232C connection (serial port of the PC) can be connected to this port, data transfer using standard software packages like X talk or ProComm is possible up to 9.6 kbps. A modem is not required.

Data Rate
The speed, measured in bits per second, at which a particular network (or other application) transmits data.

Data Services
The ability to access services such as e-mail, faxes and SMS messages using a wireless phone or communicator. Also see SMS.

DBS
Direct Broadcast Satellite. Refers to service that uses satellites to broadcast multiple channels of television programming directly to home mounted small-dish antennae.

Dead Spot
An area within the coverage area of a wireless network in which there is no coverage or transmission falls off. Dead spots are often caused by electronic interference or physical barriers such as hills, tunnels and indoor parking garages.

DECT
Digital Enhanced Cordless Telecommunications. A common standard for cordless personal telephony originally established by ETSI, a European standardization body. DECT is a system for cordless business communications.

Denial of Service
An attack that renders a site unavailable for use. Usually accomplished by bombarding a site with so many requests for information that it crashes or slows down; may also be done by interrupting network connectivity at the router or switch.

Dialed Number Identification Service
A string of digits that the telephone network passes to the ACD, VRU or other devices, to indicate which number the caller dialed. The ACD can then process and report on that type of call according to user-defined criteria. One trunk group can have many DNIS numbers.

Dial-up Line
A dial-up line is a non-dedicated communications line in which a connection can be established by dialing the number or code associated with the destination. A common example of a dial-up line, also called a switched line or public line, is the public telephone line. Dial-up lines generally support speeds of 2,400 to 9,600 bps.

DID
Direct Inward Dial, where you can dial directly into a company and reach an extension without going through a switchboard operator.

Digital Certificates
Digital certificates are used to positively identify a person or organization and it establishes their credentials when doing business or conducting other transactions on the web. A certificate authority issues a digital certificate.

Downlink
A satellite receive system that processes satellite delivered information, and includes the satellite itself, the receiving earth station and the signal transmitted downward between the two.

DSL
Digital Subscriber Line. DSL uses standard telephone lines to send high-speed Internet to homes and businesses. Local digital network loop. Always on. Download speeds up to 1.544 Mbps.

DSP
Digital Signal Processor. A DSP analyzes and processes analog signals, converting them to a digital format.

DSSS and FHSS
Direct sequencing spread spectrum (DSSS), and frequency hopping spread spectrum (FHSS) are spread-spectrum techniques that operate over the radio airwaves in the unlicensed ISM band (industrial, scientific, and medical). DSSS uses a radio transmitter to spread data packets over a fixed range of the frequency band. FHSS uses a technique by which the signal transmitted hops among several frequencies at a specific rate and sequence as a way of avoiding interference.

DTMF
Dual Tone Multi-Frequency. A system used by touch-tone telephones where specific frequencies or tones are assigned to each key, so that it can be easily identified by a microprocessor.

Dual Band
Dual Band mobile phones can work on networks that operate on different frequency bands. This is useful if you move between areas covered by different networks. For example, GSM 900 and GSM 1800.

Dual Mode
Dual mode mobile phones work on more than one network (for example, TDMA and AMPS, GSM and DECT).

Duplex
Refers to two-way communications. Full duplex is similar to th ephone in that both directions of communication occur at the same time. Half duplex is like a walkie-talkie.