A

ADSL - ADSL means Asymmetric Digital Subscribers Line. Transmission mode of the data by the phone network allowing a fast and permanent connection.

Asterisk- Asterisk is a PBX free software, multi-platform, published under license GPL per Spencer Mark of the Digium company. Asterisk allows, voice mail, conference calls, vocal servers, and a good call management. Asterisk implements protocols H323 and SIP, as well as a specific protocol named IAX (Inter-Asterisk eXchange). This IAX protocol allows the communication between a customer and an Asterisk server as well as between two Asterisk servers.

ATA - ATA or the analog telephone adaptor is the hardware device that connects the conventional telephone to the Internet through a high speed bandwidth line, provides the interface to convert the analog voice signals into IP packets, delivers dial tone and manages the call setup.

B

Backbone - A general word used to describe the core of a network, ie the main trunk routes running between different points, from which all other smaller routes originate.
Bandwidth - Bandwidth is the volume of data that can be transmitted over a communication line in a fixed amount of time. It is measured as a bit rate expressed in bits/s or multiples of it (kbit/s Mbit/s etc.).

Bandwidth - Bandwidth is the volume of data that can be transmitted over a communication line in a fixed amount of time. It is expressed in bits per second (bps) or bytes per second for digital devices and in cycles per second, or Hertz (Hz) for analog devices. Bandwidth can also be defined as the difference between a band of frequencies or wavelengths.

BLF - BLF as Busy Lamp Field is used as presence or state indicator. This option is generally used by phone equipment to allow a resource person to know at all time the status of other phones (not busy, ringing, busy, etc.)

BLI (Busy Lamp Indicator) - A light or LED on a telephone that shows which line is in use.

Broadband - It is a term used to define high speed Internet connection, generally provided by cable TV, DSL or dedicated telecom lines. The high speeds are achieved by the carrying capacity of the cable that can carry multiple messages simultaneously.

C

Cable modem - The cable modem is a device that is used to connect a computer to the high speed coaxial cable run by cable TV companies to provide access to the Internet. The connection is made through an Ethernet port, which is a shared medium and can affect download speeds if too many users log on simultaneously to the Internet on that particular cable segment. However, despite this cable modems provide Business fast access to the net.

Cache Memory - A high-speed computer memory which contains the next most likely instruction or sequence of instructions to be executed upon completion of the present instruction.

Call - A request to connect, or the connection that results from the request, either voice or data. Contrast with mini call and virtual call.

Call Accounting - The recording of data pertaining to start/end times, number of segments, NUI, NTN etc., in packet-switched networks.

Call Detail Recording (CDR) - A PBX feature where each phone call is logged by time and charges.

Called Channel - A channel that can receive but not originate calls. A calling channel can call, but not receive calls, while a called/calling channel can both originate and receive calls. These examples are found in both LAN and packet-switched networks.

Call Forwarding - A telephone service feature that can be programmed to automatically forward calls to another number.

Calling rate - The average number of calls per telephone, determined by dividing the number of busy-hour calls by the number of telephones.

Call setup time - The length of time it takes to establish a switched call between two pieces of DTE.

Call Waiting, Camp-on - Two definitions exist in normal usage:

1) A telephone service allowing a call to a busy telephone to be held while a tone notifies the busy telephone that a call is waiting.

2) In LAN environments; a facility to allow users to wait in a queue if the requested resource is busy. Users are then connected on a first come first serve basis once the resource becomes available.

Carrier - A continuous frequency, that can be impressed or modulated with a second information carrying signal.

Carrier Detect - An RS-232 interface modem signal (transmitted on pin 8) that indicates that the local modem is receiving a signal from the remote modem. Also called Data Carrier Detect (DCD) and Received Line Signal Detector (RLSD).

Carrier System - The method of transmitting a number of channels over a single path by modulating each channel on a different carrier frequency at the originating end, then demodulating at the receiving end to return the signals to their original form.

Carrier Wave - The wave upon which a signal is superimposed

Chain - A series of linked processing centers where information must pass through on a "store and forward" basis to get to final destination.

Channel - A method for one way transmission, with several definitions of common usage:

1) In and IBM system, a high speed data link that serves to connect the CPU with its peripheral devices. See Block Multiplexor and Byte Multiplexor channels.

2) In State and Federal tariffs, a path for electrical transmission between two or more points without common carrier provided terminal equipment such as a local connection to DTE . Also called a circuit, path or facility.

Channel Interface - See Channel and Interface.

Channel loopback - A diagnostic test that forms the loop at the multiplexer's channel interface . See loopback definition and the related chart in Section B.

Channel, primary - The higher speed of two channels used for transmitting. Also known as Forward or Main channel. Contrast with reverse channel.

Channel, reverse - The slower speed of two channels used for slow- speed data such as error-detection. Contrast with primary channel .

Channel Service Unit (CSU) - A device required by AT&T in order to connect a DTE to a digital transmission line for DDS . The CSU may be integrated into a Data Service Unit ( DSU).

Channel, Voice grade - A channel suitable for the transmission of speech, digital or analog data, or facsimile, typically with a frequency range of about 300 to 3300 Hz.

Character - Any letter, number, punctuation mark or other sign contained in a message, including characters for control functions and for special symbols. See also Control character.

Character Oriented - Used to describe a communications protocol that carries control information encoded in one or more bytes ( octets). Also known as byte oriented. Contrast with Bit oriented.

Character Parity - A method of adding an overhead bit to a character code to provide error-checking capability.

Characteristic Distortion - A distortion in transmission resulting from transients as a result of modulation. The levels of characteristic distortion depend upon the transmission channel and its qualities.

Character Set - A code, such as ASCII or EBCDIC used to represent data in a computer system. A collection of characters including special symbols and functions.

Circuit - In data communications, a circuit is a communications path between two points. In electronic design, a circuit is defined as one or more components that act together to perform one or more functions.

Circuit Switching - A method of communications in which physical circuits are transferred or switched to complete connections for exclusive use until the connection is released. Contrast with packet-switched networks.

Circuit switched networks - These networks have been used for making phone calls since 1878. They use a dedicated point-to-point connection for each call. This reduces their utility because no network traffic can move across the switches that are being used to transmit a call.

Centrex - Centrex is a PBX-like service providing switching at the central office instead of at the customer's premises. Typically, the telephone company owns and manages all the communications equipment and software necessary to implement the Centrex service and then sells various services to the customer.

CLEC - stands for Competitive Local Exchange Carrier. A CLEC typically builds and operates a communication network to provides its customers with an alternative to the local telephone company (ILEC).

CLI - Caller Line Identity (CLI) is the piece of information that displays on your telephone the number of the person calling. Some telephone systems are unable to pass this information. However, the majority of customers are now demanding that CLI is available as a requirement.

Codec - A term that arises from the Compressor - Decompressor or encoder/decoder process. It is used for software or hardware devices that can convert or transform a data stream. For instance, at the transmitting end codecs can encode a data stream or data signal for easy transmission, storage or encryption. At the receiving end, they can decode the signal in the appropriate form for viewing. They are most  Once a file was compressed by a codec such as MP3 or RealAudio, it is smaller and easier to transmit on the Web, but preserves a sound quality faithful to the original.

Compression - This is a term that is used to indicate the squeezing of data in a format that takes less space to store or less bandwidth to transmit. It is very useful in handling large graphics, audio and video files.

D

Data - The representation of facts, instructions or concepts in a structured manner suitable for communication.

Data Acquisition - A method of recording and measuring data from physical devices.

Database - An organized collection of information.

Data Channel - The data transmission path between two or more stations.

Data Circuit - A telecommunications medium for the transmission of information in analog or digital form.

Data Collection - A procedure where data arriving from several sources, is combined at one location in a file or queue, prior to processing.

Data Communication - The processes, facilities and equipment used to transport encode d information from one point to another.

Data compression - This is the process that is used to compress large data files into mall files so that they use less bandwidth during transmission and less disk space when stored. The compression depends upon the repeatable patterns of binary 0s and 1s. The higher the number of repeatable patters, the higher is the compression. The right compression codes can compress data files to 40% of their original size. The graphics files can be compressed even more – from 20% to 90%.

Debit - Amount of information transferred within a specified amount of time OR transfer rate.

Dial Line - Also known as dial-up line or dial-in line, any communications line that must be dialed. Contrast with Dedicated line .

Dial Network - A term synonymous with public telephone network . See also dial line.

Dibit - A grouping of two bits so that in combination there are four possible values: 00, 01, 10, 11. Each possible value of a dibit is encode d as a unique carrier phase shift (called four- phase modulation).

DID - Direct Inward Dialing (DID) which is also called Direct Dial-In (DDI) in Europe, is a feature offered by telephone companies for use with their customer's PBX systems, whereby the telephone company (telco) allocates a range of numbers all connected to their customer's PBX. As calls are presented to the PBX, the number that the caller dialed is also given, so the PBX can route the call directly to the desired person or bureau within the organization. This feature enables companies to have fewer lines than extensions, while still having a unique number for each extension that is callable from outside the company. As an example, each extension of the PBX system may be assigned a seven digit external telephone number, with a fixed four or five digit prefix. Someone who knows the internal extension of his/her correspondent can dial the seven-digit number and be connected directly to the person called, bypassing the operator or PBX auto-attendant.

Differential Phase Shift Keying (DPSK) -The modulation technique used in the Bell 201 modem. Also, see dibit .

Digit, Digital - A discretely variable signal as compared with analog, which is continuously variable. Data signals are coded in discrete and separate pulses.

Digital Data - Any information represented by digital code .

Digital Error - Digital transmission where a 0 signal is mistakenly understood to be a 1 signal.

Digital Loopback - A diagnostic technique for testing the digital circuitry of a communications device, usually a modem . The loop is formed at the modem 's DTE interface, either initiated locally or remotely via communications circuits.

Digital Service Unit (DSU) - See Data Service Unit.

Digital Switching - A process whereby a connection is established and maintained through program control. Digital information is routed between input and output.

Digital Transmission - The direct transmission of discrete pulses as opposed to analog transmission.

DISA - Abbreviation for "Direct Inward System Access" which indicates a Private branch exchange (PBX) feature in which a caller (upon entering a code through a touch-tone phone) gets another dial tone for accessing some or all of the features of the PBX, such as making an overseas call or leaving a voice mail message.

DNIS - Short for Dialed Number Identification Service, a telephone service that identifies for the receiver what telephone number was dialed by the caller. A common use for this type of system is 800 and 900 phone numbers that often channel multiple phone numbers into the same PBX system. Once the call enters the PBX system, the DNIS will identify which number was dialed and record that information.

DSL modem - A DSL modem is a device that is used to connect one or more computers to the high speed DSL line provided by a DSL operator to gain access to the Internet. The customers use these modems to log on the net to download or transmit data. Since the DSL lines have high bandwidth capacity the data transfer speeds are very high.

DTMF - Dual-Tone Multi-Frequency is a signaling type which is used for signaling over the line in the voice frequency band to the switching centre. In modern terms, it is known as Touch Tone, a form of dialing by pressing a series of numbers.

Duplex - Any communications facility providing transmission in both directions simultaneously, often referred to as "full duplex". Contrast with "half-duplex".

Duplex Transmission - The simultaneous, independent, 2-way transmission of data in both directions. Contrast with "half- duplex transmission".

Duplexing - A process using redundancy, whereby duplicate processors, files or circuitry would be available to enable the system to carry on its work. Providing an alternate system in this way is also called "Tandem".

DUV (Data Under Voice) - The normally unused spectrum at the lower end of a radio channel used to provide a T1 (1.544 m bps) channel for digital services.

E

Echo canceller - A device used to remove the echo found on a phone line as a result of delay. It can be the result of the length of the circuit being used for the call, or delay in the packets arriving at their destination in the case of VoIP. In effect, echo cancellers should be used on any long distance calls, or calls over IP or on mobile networks.

Echoplex - One method of checking data integrity by returning characters to the sending station for verification. This process requires simulated full duplex operation.

Echo Suppressor - A device used by telephone companies to block the receive side of the line during the time that the transmit side is in use.

Error - A term used to describe a deviation from the expected, especially if data integrity is jeopardized.

Error Correction - A method to insure data integrity in received data, performed by retransmission requests to the sending station (source), or by manipulating the received data. See ARQ and FEC.

Error Rate - The measure of data integrity given as the blocks, bits or characters incorrectly received, versus the number transmit ted. Error rate is sometimes seen as a rate of one error every one million bits.

Exchange - One or more central offices and equipment belonging to the telephone company designed to administer communication service to a particular area.

Exchange, Private Automatic (PAX) - A privately operated dial telephone exchange designed to prohibit calls to or from the public telephone network.

Exchange, Private Automatic Branch (PABX) - A user owned (private) automatic telephone exchange that may be a data PABX, voice PABX or voice/data PABX.

Expandor - A transducer-like device with the capability to expand the input voltages for a given range of amplitude.

Explicit Access - Contrasted with contended access, explicit access is a method of shared access found in LAN environments, allowing stations to make use of the network individually for a certain time period. Each station receives a turn, but must also wait for its turn.

Extended Addressing - A facility found in bit-oriented protocols allowing larger addresses to be used. IBM SNA adds two high- order bits to the basic address.

Extended Area Service (EAS) - A common carrier telephone service providing calls to a designated area extending beyond the local exchange .

External Modem - A modem designed to be physically located externally from the terminal device instead of internally as in an integrated modem.

F

Facility - Two definitions exist in networking technology:

1) The computer system capabilities due either to software or hardware.

2) The data communications lines and equipment required to build a circuits and transmission networks.

FAX (Facsimile Terminal) - An image transmission system designed to reproduce the communicated image (such as documents or photographs) on a paper forms.

Full duplex - The full-duplex is very often the association of two channels simplex, as a highway is the association of two roads with only one direction. The connection full-duplex can be compared with a phone conversation where the two interlocutors can speak at the same time.

FXO - FXO (Foreign Exchange Office) is a telephone interface that receives POTS. Analog telephone handsets, fax machines and (analogue) modems are FXO devices.

FXS - FXS (Foreign Exchange Station) is a telephone interface which provides battery power, sends dial tone, and generates ringing voltage. A standard telephone plugs into such an interface to receive POTS.

G

H

Handset - The part of a telephone that contains both receiver and mouthpiece.

Hardcopy - The printed output of a computer, in readable form.

Hardware - The physical equipment that comprise a computer system, including mechanical, or electromechanical devices, as opposed to the computer program. Contrast with software .

Hardware Interface - Physical hardware used in the inter connection of computer/data terminal devices and modems.

Hardwired - The permanent connection of data communications links, lines or cables and related devices.

H.323 - An ITU standard that lays down guidelines for real time voice and videoconferencing utilities on the Internet. The H.323 standard supports voice, video, data, application sharing and white-boarding and defines media gateways for conversion to packets.

Half duplex - Half-duplex can be compared with a communication with walkie-talkies, one speaks (the other cannot speak at the same time) and when he releases the button (signal of end of conversation) the other can then speak.

I

IAX - IAX (Inter-Asterisk eXchange) is the protocol native to Asterisk PBX and supported by a number of other softswitches and PBXs. It is used to enable VoIP connections between servers as well as client-server communication. IAX now most commonly refers to IAX2, the second version of the IAX protocol. The original IAX protocol has been deprecated almost universally in favor of IAX2.

ILEC - An ILEC is the traditional telephone company. ILEC stands for Incumbent Local Exchange Carrier. In the U.S., the Regional Bell Operation Companies (RBOCs) were formed after the divestiture of AT&T. The Independent Operating Companies (IOCs) located in single cities or rural areas are commonly referred to as ILECs.

IM - IM, which stands for Instant Messenging, is a software that allows users to exchange messages in real time. However, to do so both the users must be logged on to the instant messaging service at the same time. Some of the popular IM services are: MSN Messenger, AOL Instant Messenger, Yahoo! Messenger, Google Talk and ICQ.

Internet congestion - Internet congestion occurs when a large volume of data is being routed on low bandwidth lines or across networks that have high latency and cannot handle large volumes. The result is slowing down of packet movement, packet loss and drop in service quality.

IP address - An IP address, also known as Internet Protocol address, is the machine number used to identify all devices that are connected to the net. Each device has its own unique number which it uses to communicate. This number is fixed in the case of those computing devices that have a fixed IP address. The rest are allotted a dynamic IP address, which is valid for the period they are connected to the net. The numbers range from 0.0.0.0 to 255.255.255.255.

IP PBX - An IP PBX is a private branch exchange (telephone switching system within an enterprise) that switches calls between VoIP users on local lines while allowing all users to share a certain number of external phone lines. The typical IP PBX can also switch calls between a VoIP user and a traditional telephone user, or between two traditional telephone users in the same way that a conventional PBX does. The abbreviation may appear in various texts as IP-PBX, IP/PBX, or IPPBX.

IP mapping - IP mapping is the process of identifying IP addresses on the basis of their geographical locations. The mapping enables web administrators to pinpoint the location of any computing device connected to the Internet.

IP Phone - An IP phone is one that converts voice into digital packets and vice versa to make phone calls over Internet possible. It has built-in IP signaling protocols such as H.323 that ensure that the voice is routed to the right destination over the net. The IP phones come with several value added services like voicemail, e-mail, call number blocking etc.

IP telephony - IP telephony refers to the two-way transmission of voice over Internet. The voice is transmitted in real time by using the packet-switched technology over the IP network. Some of the applications that use IP telephony are IP-based phone services, voice over instant messaging and videoconferencing.

IP - IP, which is the acronym for Internet Protocol, defines the way data packets, also called datagrams, should be moved between the destination and the source. More technically, it can be defined as the network layer protocol in the TCP/IP communications protocol suite.

ISP - Internet Service Provider (ISP) determines any service provider proposing the access to Internet and some complementary services. ISP connects to its customers using a data transmission technology appropriate for delivering Internet Protocol datagrams, such as dial-up, DSL, cable modem or dedicated high-speed interconnects.

ITU - ITU, which is the acronym of International Telecommunication Union, is a telecommunications standards body based in Geneva. It works under the aegis of the United Nations and makes recommendations on standards in telecommunications, information technology, consumer electronics, broadcasting and multimedia communications.

IVR - Interactive Voice Response is a software application that accepts a combination of voice telephone input and touch-tone keypad selection and provides appropriate responses in the form of voice, fax, callback, e-mail and perhaps other media. IVR is usually part of a larger application that includes database access. Common IVR applications include: bank and stock account balances and transfers, surveys and polls, caller authorization centers, etc

J

Jabber, Jabbering - The flow of continuously sent garbage from a failed terminal, resulting in a lockup of a LAN for other users.

Jack - Either a three-conductor or a "mini-plug", RJ11 type receptacle designed to accept the corresponding plug for an electrical connection.

Jamming - The disturbance or interference of open-air radio transmission to deliberately prevent communication.

Jitter - It is a term used to indicate a momentary fluctuation in the transmission signal. This happens in computing when a data packet arrives either ahead or behind a standard clock cycle. In telecommunication, it may result from an abrupt variation in signal characteristics, such as the interval between successive pulses.

K

Ka Band - The frequencies used for satellite communications, approximately in the 30/15 gHz range.

kbps (Kilo Bits Per Second) - Thousands of bits per second (BPS) equal to 10 to the third power. See also BPS.

Keying - A method of encoding data by modulating the carrier either by phase or frequency.

kHz (kilo Hertz) - Abbreviation for 1000 Hertz (cycles per second). See also Hertz.

KSR (Keyboard Send and Receive) - A teleprinter transmitter and receiver that can only transmit from the keyboard. Contrast with RO and ASR devices.

Ku Band - The frequencies used for satellite communications, approximately in the 14/12 gHz range.

L

Lag - Is the term used to indicate the extra time taken by a packet of data to travel from the source computer to the destination computer and back again. The lag may be caused by poor networking or by inefficient or excessive processing.

Latency - Latency is the time that elapses between the initiation of a request for data and the start of the actual data transfer. This delay may be in nanoseconds but it is still used to judge the efficiency of networks.

Leased Line, Private Line, Dedicated Line - A point-to-point or multipoint communications line for voice/data leased from a common-carrier, usually on a monthly basis.

LCR - Least Cost Routing (LCR) is a system that allows to select among several telecom operators, proposing the best road, for each call, according to several criteria such as the cost for the called destination and quality. LCR system is used by the operators for the management of their voice traffic, but also by certain companies wishing to optimize their costs of telecommunications.

Line Driver, Local Dataset - A DCE device that functions as a signal converter, "driving" the digital signal directly across a communications path. Oftentimes, line drivers are used to ensure reliable transmission beyond the 50-foot RS-232 limit. Also known as short-haul modems.

Line Speed -The maximum, reliable, rate of transmission, dependent upon the capability of a modem, expressed in bps.

M

Mapping - The process of identifying all related data fields or data streams and putting them in an easily identifiable context. For example, IP mapping enables users to pinpoint the geographical location of any computing device on the Internet.

Mbps - for Mega bits per second. A flow of a million bits a second.

MGCP - Acronym of Media Gateway Control Protocol. Used for a Voice over IP system. It consists of a Call Agent and a set of gateways, of which at least one works as the "media gateway" and performs the conversions.

Microcomputer - A small desktop or lap-top computer often called a personal computer.

Microprocessor - The processing unit of a microcomputer, sometimes called a "computer-on-a-chip".

Microprogramming - The practice of building a program into ROM to carry out functions otherwise contained on a storage device and processed at a substantially slower speed.

Microsecond - One millionth of a second.

Modem - A device named from the contraction of the words "modulator - demodulator" and used to convert serial digital data from a transmitting terminal to a signal suitable for transmission over a telephone line. The term may be used when the modulator and demodulator are physically in the same signal-conversion equipment, since the device must also reconvert the signal to serial digital data for the receiving terminal.See also data set.

Modem Eliminator - A device designed to connect two DTE devices. Modem eliminators perform the necessary signal conversions and may occasionally provide clocking. Modified cables called "crossover cables" or connector "adapters" could also provide this function.See null modem.

Modem, High Speed - A modems operating in excess of 4800 bps on voice-grade lines.

Modem, Multiport - A modem / multiplexer combination that allows two or more DTE's to be connected to the same line, also known as split-stream modem.

Modem, Quick Turnaround - A modem designed with minimal turnaround time for use in half-duplex operation. Also known as QP (quick poll) and FP (fast poll).

Modem, Short Haul (SHM) - See line driver.

Modem, Wide Band - A modem designed to achieve bit speeds greater than the high speed modem, speeds of 19.2 kbps or 56 kbps. Wide band modems require wide band circuits and will not operate over a voice grade circuit.

N

Nanosecond - One billionth of a second.

NANP - Stands for North American Numbering Plan. A telephone numbering system that has evolved the way area codes and numbers are allotted. The system was established in 1947 and covers the United States, Canada and a few neighboring areas. It uses a three-digit area code and seven-digit telephone numbers. Its fiat is, however, limited to the public switched telephone networks only.

Net Phone - A net phone uses the Voice over IP technology to make voice calls. These calls are made by converting analog sound signals into digital data packets, and then moving the packets to their destination over the net.

O

Off-Hook - An activated telephone set or a modem automatically answering a call. Contrast with on-hook.

Off-Line, Offline - Any equipment or devices not accessible to the CPU . Also, any terminal equipment not connected to a transmission line. Contrast with online.

Off Loading, Off Loaded - A process whereby a device is relieved of certain processing tasks, so that another (possibly less expensive) device can fill in those duties. Example: a FEP offloads a host processor or a terminal may off load a concentrator.

Off-Net - A term used to define any location that is beyond the primary serving area of a DDS. Contrast with on-net.

On-Hook - A deactivated telephone set or a modem that is not in use. Contrast with off-hook.

On-line, Online - Any computer equipment or devices that are accessible to the CPU. In the case of an online system, input data can enter the computer directly from their point of origin, or output data can be transmitted directly to where they are to be used.

On-Net - A term used to define any location that is beyond the primary serving area of a DDS. Contrast with off-net.

P

Packet - In network, a packet is a data transmission unit used to communicate. In order to transmit a message of a machine to another on a network, this one is cut out in several separately transmitted packages. A package includes the data, encapsulated in a header, including/understanding useful information to transport and decode the message.

Packet loss - Packet loss is the term used to indicate the loss of data packets during transmission over a computer network. This may happen on account of high network latency or on account of overloading of switches or routers that are unable to process or route all the incoming data.

Packet switched networks - These are networks that break messages into small digital packets, stamp each packet with the destination IP address, and route them across different channels to their destination where they are reassembled in their proper sequence. This is done to avoid network congestion and speed up data movement from multiple sources.

Packet Terminal - Any DTE device able to transmit and receive packets.

Peer-to-Peer (P2P) - The term peer-to-peer is used to indicate a form of computing where two or more than two users can share files or CPU power. They can even transmit real time data such as telephony traffic on their highly ad hoc networks. Interestingly, the peer-to-peer network does not work on the traditional client-server model but on equal peer nodes that work both as "clients" and "servers" to other nodes on the network.

POP - A point-of-presence (POP) is an artificial demarcation point or interface point between communications entities.

Portability - Fact of changing mobile operator while preserving your phone number.

POTS - This abbreviation for "Plain Old Telephone Service" refers to the standard analog telephone service without extra enhancements. It remains the basic form of residential and small business service connection to the telephone network in most parts of the world but is now opposed to more advanced forms of telephony such as ISDN, mobile phones and VoIP.

Private Network - A user maintained voice/data network generally characterized by a mixture of different vendor's equipment.

Processor drain - This is a term used to indicate a drop in the quality of VoIP phone service when a user opens several applications on his computer simultaneously.

Profile - A term used in packet-switched environments to describe a set of parameters or values defining a hardware device (printer, terminal) that would be stored and later recalled as a group for later use.

Program - The specific sequence of computational steps in a programming language. A set of instructions for a computer to perform.

Programmable Terminal - A computer terminal that contains memory and has processor capability, also known as an intelligent terminal.

Protocol - It is a convention or standard that defines the procedures to be adopted regarding the transmission of data between two computing end points. These procedures include the way the sending device should sign off a message or how the receiving device should indicate the receipt of a message. Similarly, the protocols also lay down guidelines for error checking, data compression, and other relevant operational details.

PSTN - PSTN, which stands for Public Switched Telephone Network, refers to the telephone system that transmits analog voice data. Till recently, PSTN was the heart of all phone systems worldwide. However, most of the developed world is now switching to or has switched to telephone networks that are based on digital technologies, such as ISDN and FDDI.

Q

Queue - A "waiting line" of items or units, such as messages, waiting to be serviced.

Queuing, Queuing Theory - A process allowing transactions to be serviced and specifies each of the following elements:

1) Source- The electronic signals of a data communications system.

2) Input Process- The statistical pattern by which the data arrives at the service facility, also called "random arrivals".

3) Queue Structure- The actual "waiting line", which may consist of one queue or several queues. The line(s)" may be conceptual rather than physical, such as the case of remote terminals waiting to be polled by a computer.

4) Service Facility- One or more service channels in parallel, attached to one or more servers in series.

5) Service Process- The time required to completely service a unit waiting in a queue. The time is determined by probability formulas.

6) Service Discipline- The rules by which units are selected and serviced. Service may be FIFO (first in, first out), random, or according to some priority procedure.

R

RAM (Random Access Memory) - A storage device into which data may be entered and read, usually (but not always) a volatile semiconductor memory.

Real Time, Real-Time System - A real-time system responds immediately at the time a transaction occurs, unlike a batch processing system which would produce journals, reports, and other outputs according to prescheduled batch processing cycles. Real-time systems in which there is rapid and frequent interaction between human and machine are sometimes said to operate in a "conversational" mode.

Receive, Receiver - The process or device assigned to receive messages in a data communications network, usually, but not always, at a DTE device.

Routing - The communications path assigned to a telephone call to reach the calls destination.

Routing, Alternate - The backup, or secondary path to a calls destination, used in the event of link failure or component breakdown.

Routing Code - The code prefix of telephone numbers used for international calling or long distance domestic calls (area codes, for example).

Routing Indicator - The destination address of a computer device, found in a messages header, to which the message must be delivered.

RTP - RTP (Real-Time Transport Protocol) is commonly used with IP networks. RTP is designed to provide end-to-end network transport functions for applications transmitting real-time data, such as audio, video, or simulation data, over multicast or unicast network services. RTP provides such services as payload type identification, sequence numbering, time stamping, and delivery monitoring to real-time applications.

S

Sampling - This is a methodology used to measure the value of an analog signal at regular intervals, and encoding it into a digital format for VoIP phone services.

Security - Any method or technique designed to prevent unauthorized physical access to information. Wiretapping or electromagnetic eavesdropping is a security threat whenever data travels through the air or over wires that are not in a secure area. Most data communication networks use common carrier facilities, and this presents problems. Sensitive data that is to be transmit ted from one location to another should be encrypted to make it private. Privacy transformations involving static methods of coding require a certain amount of work to break, but can usually be decoded after some effort. The best coding techniques involve keys that are as long as the data to be encrypted. By using different starting values, and different related sequences of random numbers, it becomes very difficult to determine the generating algorithm from eavesdropping, so the required work to break the code is very extensive.

Service provider - A service provider is a business entity that provides a communication, storage or processing service for a fee. Some of the service providers in the digital world are the Internet service provider (ISP), application service provider (ASP), storage service provider, mobile phone service provider, web hosting provider, and of course, VOIP service provider.

SIP - SIP, which is the acronym of Session Initiation Protocol, is an IP telephony signaling protocol. It is primarily used for voice over IP (VoIP) calls, though with some extensions it can also be used for instant messaging. It is less complex than H.323, the other IP telephony protocol. [edit] SIP (Session Initiation Protocol)

SIP Client - An RTC (real-time communications) client that uses SIP (Session Initiation Protocol) to establish and maintain RTC sessions with a SIP server.

SIP Server - A server that uses SIP (Session Initiation Protocol) to manage real-time communication among SIP clients.

Skewing - The time delay between two data signals.

SNA (Systems Network Architecture) - An IBM system product offering the computer user a total data processing and data communications system for IBM software and hardware devices. End users are unaffected and independent of the specific data communications system services. SNA 's system functions are separated into three discrete areas: application layer, functional management layer, and transmission subsystem layer.

Softphone - This is a software application that is installed in the user’s PC. It uses the Voice over IP technology to route voice calls over the net and provides several value added features, such as call forwarding, conference calling, and integration with applications such as Outlook for automatic dialing. The audio is provided through a microphone and speakers plugged into the sound card. The only limitation of a Softphone is that the phone call has to be made through a PC. Many softphone are free VOIP software downloads.

Soft switch - It is a software application that is used to keep track of, monitor or regulate connections at the junction point between circuit and packet networks. This software is loaded in computers and is now replacing hardware switches on most telecom networks.

T

T.38 - T.38 is an International Telecommunication Union (ITU) recommendation for allowing transmission of fax over IP networks in real time.

Telecommunications - The transmission (and reception) of signals producing sounds, images or information using a variety of media such as fiber optic, copper wire, infrared or radio frequency.

Termination - Call Termination, also known as voice termination, refers to the handing off or routing of telephone calls from one telephone company, also known as a carrier or provider, to another. The terminating point is the called party or end point. The originating point is the calling party who initiates the call. This term often applies to calls while using VoIP: a call initiated as a VoIP call is terminated using the PSTN. In such cases, termination services may be sold as a separate commodity. The opposite of call termination is call origination, in which a call initiated from the PSTN is terminated using VoIP. Thus, in "origination" a call originates from PSTN and goes to VoIP, while in "Termination" a call originates in VoIP and terminates to PSTN.

Transceiver - A device that can function as both a transmitter and a receiver.

Transmission - The sending of information over a data communications medium.

Transmission Block - A grouping of data characters, bytes, flowing through the transmission channel, over which a synchronization coding pattern has been applied for timing purposes or for error control.

Transmission Speed - A measure of how quickly data is being transmit ted, usually expressed in bps, although commonly, but incorrectly, expressed in baud.

Transmit - To send out a signal over data communications media such as optical fiber, copper wire, or via radio waves through the atmosphere, from one station to another.

Trunk - A communications channel between two points, typically referring to large-bandwidth telephone channels between switching centers that handle many simultaneous voice and data signals.

U

UART (Universal Asynchronous Receiver/Transmitter) - A microchip device performing asynchronous communication functions by converting parallel digital output from a DTE device into bit serial transmission (and bit serial into parallel).

UHF (Ultra High Frequency) - The range of frequencies, spanning between 300 mHz and 3 gHz, used for cellular radio frequencies (RF) and for UHF television channels 14 through 83).

ULSI (Ultra Large Scale Integration) - A term describing an ultra- high density microchip containing over 10,000 circuits.

Unattended Mode, Unattended Operations - A term used to describe an automatically operating communications device, such as an auto- answer modem.

Unbalanced, Unbalanced To Ground - A term used to describe the condition present in a two wire circuit when the impedance-to- ground on one wire is different from that of the other. Contrast with balanced, balanced-to-ground.

Unbundling - A term used to describe the itemization of common carrier or vendor provided communications services.

Uncontrolled Terminal - A computer terminal containing no polling or control logic and is always online to the CPU.

Uninet - A data communications common carrier offering an X.25 PDN.

Unix - An AT&T proprietary operating system designed for multi- user, multi-tasking data communications operating systems .

UPC (Universal Product Code) - The "bar code" used to identify consumer and industrial products in mechanized inventory systems.

Uptime - The period of time that a computer application or data communications link would be available to the user community on an undegraded, and uninterrupted basis. Contrast with downtime.

Upward Compatible - An application program having the characteristics of compatibility with an enhanced mode or operation (such as a newer release or version operating system).

USART (Universal Synchronous/Asynchronous Receiver/Transmitter) - A semiconductor device performing synchronous/asynchronous conversion from a communications processor to the correct format for data transmission.

USASCII (United States of America Standard Code for Information Interchange) - See ASCII.

USRT (Universal Synchronous Receiver/Transmitter) - A semiconductor device that formats data for communications over a synchronous data circuit.

Utility, Utility Program - A computer program designed to perform a task required by many or most of the computing systems users, the most common of which are those that copy information from one medium to another and those used to streamline an operation.

V

Virtual fax - A virtual Fax is an Internet based fax service enabling you to send and/or receive faxes by email. The faxes sent to you will be converted into a digital format sent directly to your email. This allows communication by fax without needing a fax machine.

Virtual Number - A telephone number outside of the physical area code you reside in. Provided by telephone carriers and VoIP providers, it allows callers to make local calls from that area code to your phone. For example, if you live in Atlanta and have a virtual phone number with a San Francisco area code, anyone calling from San Francisco is making a local call.

Voicemail - It is a telephone messaging system that digitizes the analog voice signals and stores them on disk or flash memory in a central computer. These messages can then be retrieved by users by logging on to the server or forwarded to another voice mailbox. Most voice mail systems have auto attendant capabilities, that is they can use prerecorded messages to route callers to the appropriate person or mailbox. Voicemail is usually a free feature in VOIP service plans.

VOIP Gateway - This device provides the conversion interface between the public switched telephone network (PSTN) and an IP network for voice and fax calls. Its primary functions include: voice and fax compression/decompression, packetization, call routing and control signaling. It also provides an interface to Gatekeepers or Softswitches, billing systems, and network management systems.

VOIP PBX - VoIP PBX, which stands for Voice over Internet Protocol Private Branch eXchange, is a telephone switch that converts IP phone calls into traditional circuit-switched TDM connections. It also supports traditional analog and digital telephones.

VOIP Phone - A VoIP phone is one that uses the Internet to route voice calls by converting the voice data into IP packets and vice versa. The phones come with built-in IP signaling protocols such as H.323 or SIP that help in the routing of data to the right destination. A VoIP phone can also be a software application that is installed in the user's PC. In this case it is known as the Softphone. Also, the calls in this case have to be made from the PC, and not through a telephone instrument.

VOIP services - The VoIP services are packet-based services that use the Internet to move voice data. These services are much cheaper than the traditional PSTN services because the investment in infrastructure is low. They also come with several value added features which make them more lucrative than the conventional landline phone services.

VoIP Trunking - Service providers can use this application to connect enterprise and call center customers directly to their VoIP network. By bypassing local operators and toll charges, the VoIP Trunking application enables service providers to offer attractive termination rates for both domestic and international long distance calling. This application connects seamlessly to the enterprise/call center's PBX, allowing employees to make off-net calls at reduced rates.

W

WAN (Wide Area Network) - A term used to describe a data communications network using common carrier circuits to connect stations and processors. Contrast with LAN.

X

XON-XOFF - See flow control.

Xerox - The corporation credited as the originator of Ethernet .

XMODEM - A communications protocol devised by Ward Christiansen to perform simple error checking between microcomputers . XMODEM is a half-duplex protocol, used on full-duplex circuits transmitting 128 characters per block. After information is sent, the sender waits for a reply before transmitting the next message.

XNS/ITP (Xerox Network Systems'/Internet Transport Protocol) - A communications protocol used in a LAN environment between networks, functioning similar to the TCP/IP.

Y

YMODEM - A communications protocol very similar to XMODEM designed to perform simple error checking between microcomputers . YMODEM is a half-duplex protocol, used on full-duplex circuits transmitting a 1 kilobyte (1,024) characters per block. After information is sent, the sender waits for a reply before transmitting the next message.

Z

Zero Code Suppression - The practice of suppressing the transmission of eight of more consecutive binary "0" bits by inserting a binary "1" bit. Zero code suppression is used with digital T1 and related communications facilities.

Zero Insertion - A practice used in an SDLC environment that includes a binary "0" in a stream of transmitted data to avoid confusing SYN characters with data characters. The receiving end removes the inserted zeros.

Zero Transmission Level Point - A point of reference (0 TLP) used to measure signal power gain/loss of a data circuit.

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