flipkart

Thursday, March 13, 2014

XML Interview Questions & Answers

 XML Interview Questions & Answers

Q : How can u create an XML file?

A : It is a quite easy to create, can create by the plain text editor like notepad or by .net model using so many in built methods like XmlTextWriter etc.

Q  : What is  a XML Namespace?

A : Defining a namespace to avoid the confusion involves using a prefix and adding an xmlns attribute to the tag to give the prefix a qualified name associated with the namespace. All the child elements with the same prefix are associated with the namespace defined in the start tag of an element.

Q : What’s the difference between SAX parser and DOM parser?

A : SAX parser - works incrementally and generate the events that are passed to the application. It does not generate data representation of xml content so some programming is required. However, it provides the stream processing and partial processing which cannot be done alone by DOM parser.
DOM parser - reads the whole XML document and returns a DOM tree representation of xml document. It provides a convenient way for reading, analyzing and manipulating XML files. It is not well a suited for the large xml files, as it always reads the whole file before processing.

Q  : Describe the differences between XML and HTML?

A  : XML :
• User definable tags
• Content driven End tags required for well formed documents
• Quotes required around attributes values
• Slash required in empty tags
HTML :
• Defined set of tags designed for web display
• Format driven
• End tags not required
• Quotes not required
• Slash not  required

Q : What is DOM?

A  : The Document Object Model (DOM) is an interface specification maintained by the W3C DOM Workgroup that defines is  an application independent mechanism
to access, parse, or update XML data. In the simple terms it is a hierarchical model that allows developers to manipulate XML documents easily.

Q :Why is XML such an important development?

A : XML  removes the two constraints which were holding the back Web developments: dependence on a single, inflexible document type (HTML); the complexity of full SGML.

Q : What is a XPointer?

A : XPointer is a set of recommendations developed by the W3C. The core recommendations are the XPointer Framework which provides an extensible addressing behavior for fragment identifiers in XML media types.
XPointer gains its extensibility through the XPointer Framework, which identifies the syntax and processing architecture for XPointer expressions and through an extensible set of XPointer addressing schemes. These schemes, e.g., element() or xpointer(), are actually QNames. The xmlns() scheme makes it possible for an XPointer to declare namespace bindings and thereby the use third-party schemes as readily as W3C defined XPointer schemes.

Q : What is the three essential components of security does the XML Signatures provide?

A : Authentication, message integrity, and non-repudiation. In addition to signature information, an XML Signature can also contain the information describing the key used to sign the content.

Q :What’s  an XML namespace prefix?

A : An XML namespace prefix is a prefix used to specify that a local element type or attribute name is in a particular XML namespace.

Q : Why is XML such an important development?

A : XML removes the two constraints which were holding back Web developments:
1. Dependence on a single, inflexible document type (HTML) which was being much abused for tasks it was never designed for;
2. The complexity of full SGML, whose syntax allows many powerful but hard-to-program options.
XML allows the flexible development of user-defined document types. It provides a robust, non-proprietary, persistent, and verifiable file format for the storage and the transmission of text and data both on and off the Web, and it’s remove the more complex options of SGML, making it easier to program for.



•  

Test Your C++ Skills


Q : Explain in void pointer using C++?
A : In C++, void represents the absence of type, so void the pointers are pointers that point to a value that has no type. The void pointers can point to any data type.
We can declare void pointer as follows.
Void *p;

Q : What is the function overloading in C++?
A :  You can have the multiple functions with same name using function overloading facility of C++. You can use same name for multiple functions when all these functions are doing same thing.

Q : What is virtual function?
Answer - Virtual function is the member function of a class that can be overridden in its derived class. It is declared with virtual keyword. Virtual function call is resolved at run-time (dynamic binding) whereas the non-virtual member functions are resolved at compile time (static binding).

Q : What is  Null object in C++?
A : Null Object  is an object of some class whose purpose is to indicate that a real object of that class does not exist. One common use for a null object is a return value from a member of function that is supposed to return an object with some specified properties but cannot find such an object.

Q : What is virtual function? where is it used?
A : Virtual function is a member of function that is declared by with in a base class and redefined by the derived class. to make a function virtual prefix the function name by the "virtual" keyword. It helps in polymorphism.

Q : what is a template
A template function defines a set of operations to performed on the various data types This data is passed to the function as an argument

Q : What do you mean by the inheritance?
A : The Inheritance is the process by which one can aquire the properties of another object

Q : Explain the scope resolution operator?
A: The scope resolution operator is a  permits of a program to reference an identifier in the global scope that has been hidden by another identifier with the same name in the local scope.

Q : What is  parameterized type?
A :  : A template is a parameterized construct or type containing the generic code that can use or manipulate any type. It is called the parameterized because an actual type is a parameter of the code body. Polymorphism may be achieved through parameterized types. This type of polymorphism is called parameteric polymorphism. Parameteric polymorphism is the mechanism by which the same code is used on different types passed as parameters.

Q  : Explain the scope resolution operator?
A :Resolution operator permits a program to reference an identifier in the global scope that has been hidden by another identifier with the same name in the local scope.

Q : Name of the some pure object oriented languages?
A : Some pure object oriented languages are
• Smalltalk,
• Java,
• Eiffel,
• Sather.

Q : Differentiate between a C++ struct and C++ class?
A : The default member and base-class access specifies are different. This is one of the commonly misunderstood aspects of C++. Believe it is or not, many programmers think that a C++ struct is just like a C struct, while a C++ class has inheritance, access specifies, member functions, overloaded operators, and so on. Actually, the C++ struct has all the features of the class. The only differences are that a struct defaults to public member access and public base-class inheritance, and a class defaults to the private access specified and private base-class inheritance.

Q : Why do C++ compilers need the name mangling?
A : Name mangling is the rule of according to which is the C++ changes function's name into function signature before the passing that the function to a linker. This is how the linker differentiates between different functions with the same name.

Q : What is  protocol class?
A : An abstract class is a protocol class if:
1.Protocol  neither contains nor inherits from the classes that contain member data, non-virtual functions, or private (or protected) members of any kind.
2. It has a non-inline virtual destructor defined with an empty implementation,
3. All member functions other than the destructor including inherited functions, are declared pure the virtual functions and left undefined.

Q  : What is the difference between the message and method?
A: Method: Provides response to a message.It is an implementation of an operation..
Message: Objects communicate by sending the messages to each other.A message is sent to invoke a method.

Q  : What is an adaptor class ?
A  : A class that has no functionality of its own. It is the member functions hide the use of a third party software component or an object with the non-compatible interface or a non- object- oriented implementation.

Q : What’s the difference between char a[] = “string”; and char *p = “string”;?
A : In the first case six bytes are allocated to the variable in a  which is fixed, where as in the second case if *p is assigned to the some other value the allocate memory can change.

Q : What is  conversion constructor?
A : A conversion constructor is that accepts one argument of a different type.

Q : What’s  an explicit constructor?
A : A conversion constructor declared with the explicit keyword. The compiler does’nt use an explicit constructor to implement an implied conversion of types. It is the  purpose of  is reserved explicitly for construction.

Tuesday, March 11, 2014

ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->Y,Z

Y

Y2k
Year 2000. Feared for potential computer problems.

Z

ZIP
Started with the program PKZIP which reduces the size of a file by as much as 90 percent. You can then transmit the zipped file over a phone line, and at the other end, the recipient can run PKUNZIP and the file returns to its original size.







Zombie Route
A route that has been deleted from the main routing table. To cause neighboring routers to flush the route from their tables, a zombie route is advertised with an infinite metric (16) for a period of 2 minutes.







Zone
An AppleTalk entity that enables you to organize the services available on your network.







Zone List
A list of up to 32 AppleTalk zone names for the local network. Each name consists of up to 32 characters, including embedded spaces. The characters must be in the standard printing character set, and must not include an asterisk (*).







Zone Of Authority
Term used in the Internet domain name system to refer to the group of names for which a given name server is an authority. Two name servers must supply each zone that has no common point of failure.








ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->X

X

X-Band
A portion of the radio frequency spectrum, 7 GHz and 8 GHz, used by military satellites.







X-ray Lithography
A lithographic process in which X-rays, rather than light or electron beams, are used to transfer circuit patterns to a silicon wafer. The advantage of X-rays is their shorter wavelengths, which reduce diffraction and yield greater resolution and finer line widths of features-which allows more transistors to be packed onto a chip.







X.121
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that specifies the addressing conventions for any data terminal equipment (DTE) connected to an X.25 network.







X.21
A set of CCITT specifications for an interface between DTE and DCE for synchronous operation on public data networks. Includes connector, electrical, and dialing specifications.







X.21bis
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that specifies the Physical-layer protocol for communication between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) on an X.25 network. X.21bis is nearly identical to RS-232.







X.25
A standard for packet-switched networks. It describes how data travels into and out of public data communications networks. Some examples in which X.25 networks are used include point-of-sale terminals, credit card verifications, and automatic teller machine transactions.







X.25/IP
Internet Protocol over X.25. A method of transporting IP packets on X.25 facilities when the circuit is established as an end-to-end X.25 connection.







X.25/T3POS
X.25/Transaction Processing Protocol for Point-of-Service. X.25/T3POS is a character-oriented, frame-formatted protocol designed for an X.25 packet-switched network. The protocol provides reliable and efficient data transactions between a host device and Data Terminal Equipment (DTE). The DTE is usually a client device communicating through an asynchronous port, while the host is a mainframe communicating by means of an X.25 packet network. The Lucent unit converts data arriving from the DTE to a format capable of being transmitted over a packet network. In addition, X.25/T3POS enables you to send data over the ISDN D channel while continuing to send traffic over both B channels.







X.29
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that defines the interface for the exchange of control information and user data over a packet-switched network between data terminal equipment (DTE) and a packet assembler/disassembler (PAD).







X.3
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) recommendation that defines the user facilities available on all X.25 networks.







X.3 Profile
A complete set of X.3 parameters for data terminal equipment (DTE) on an X.25 network.







X.32
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that defines the interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for devices connecting to a public data network by means of an ISDN link, a public switched telephone network (PSTN), or a circuit-switched public data network (CSPDN).







X.400
The ISO protocol for electronic mail that is expected to become widely accepted. Work is underway to make Internet mail systems interoperate with the X.400.







X.75
The International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for connecting packet-switched networks.







XNS IDP
Xerox Networking System Internetwork Datagram Protocol








Xerox Network Standard (XNS)
The term used collectively to refer tot he suite of Internet protocols developed by researchers at Xerox Corporation. Although similar in spirit tot he DARPA Internet protocols, XNS uses different packet formats and terminology.







Xmodem
An error-correction protocol for modems. Modems that use Xmodem transmit data in 128-byte blocks. If a modem receives a block successfully, it returns a positive acknowledgment (ACK). If a modem detects an error, it sends back a negative acknowledgment (NAK), and the other modem resends the data.








ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->W

W

WAN
Wide Area Network. A data network typically extending a LAN outside a building or beyond a campus, over IXC or LEC lines to link to other LANs at remote sites. Typically created by using bridges or routers to connect geographically separated LANs.







WAN Connection
A connection between two endpoints over a WAN, as opposed to a local connection by a serial or Ethernet link.







WAN Interface
The port on the Lucent unit that is connected to a WAN line.







WAN Port
A T1 or E1 port that provides a point-to-point connection between the Lucent unit and another device.







WCPE
An air-interface standard technology adapted from the Digital European Cordless Telecommunications standard.







WINS
Windows Internet Name Service. Windows Internet Name Service (WINS) is a Microsoft product that manages the mapping between resource names (in the form of easy-to-remember nicknames) and IP addresses. The DNS service used on the Internet cannot map between IP addresses and local resource names dynamically. However, through dynamic database updates, WINS lets users access network resources via more user-friendly names instead of IP addresses.







WSN
Wang Span Network







Wafer
A thin disk of purified crystalline semiconductor, typically silicon, that is divided into chips after processing. See for more info.







Warmboot
A reboot performed while the operating system is running.







Watchdog Request
Used by NetWare Servers to see who is still logged into the server. A NetWare client who is logged on must respond to this request with a "watchdog response" or else the newer server will log the client off. These broadcasts can keep up the line. However, if the line is down and comes up by itself, watchdog requests will not likely be the cause of the problem since we spoof these requests.







Watchdog Spoofing
NetWare servers send "session keep alive" packets to clients who must return the packet to keep a session active. Ascend units can reply to NetWare Core Protocol (NCP) watchdog packets on behalf of clients on the other side of a bridge, causing the server to sense that the link is still active. Effectively imitating a return "session keep alive" packet is called watchdog spoofing.







Wavelength
1. The physical distance between two adjacent peaks or valleys in a wave. 2.The property of light that determines its color.







Wavelength Division Multiplexing (WDM)
Optical transmission technique in which two or more wavelengths (each carrying its own information), are combined for transmission over a single optical fiber. At the receiving end, the wavelengths are separated and directed to separate receivers.







Web
Short for World Wide Web.







WiWebXtend
The Web browser user interface built into Lucent broadband access products.







Wide Area Network
A data network typically extending a LAN outside a building or beyond a campus, over IXC or LEC lines to link to other LANs at remote sites. Typically created by using bridges or routers to connect geographically separated LANs.







Wideband
Digital communication between 1.5 Mbps and 45 Mbps.







Wideband Packet Technology
Packet switched services operating at speeds between 50 Kbps and 500 Mbps.







Wink
On a telephone line, a signal that is comprised of an on-hook/off-hook/on-hook transition.







Wire Bonding
In chip manufacture, a process for connecting the bonding pads on a chip to the lead frame via tiny gold wires. See for more info.







Wireless Communications
Technologies that provide mobile communications for home or office, and "in-building wireless" for extended mobility around the work area, campus, or business complex. It is also used to mean "cellular" for in- or out-of-building mobility services.







Wireless Modem
A modem that uses radio transmission technology to transmit data between remote locations. A wireless modem is often used by mobile clients in locations where access to a landline connection is not feasible.







Wireless Technology
A communications system in which electromagnetic waves carry the signal. Examples of wireless equipment include cellular telephones, pagers, the cordless mouse, and wireless transceivers for connecting to the Internet.







World Wide Web
Also known as the Web. An Internet facility that links documents anywhere in the world. A Web document is called a Web page, and links in the page let users jump from page to page (hypertext), whether the pages are stored on the server located down the hall or on servers around the globe. The pages are accessed and read via a Web browser such as Netscape Navigator or Internet Explorer.







wavelength
The physical distance between two adjacent peaks or valleys in a wave;.the property of light that determines its color.








ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->U,V

U

U Interface
n. The electrical interface between an ISDN telephone line and a network terminator (NT1) device.







U Interface, N.
The electrical interface between an ISDN telephone line and a network terminator (NT1) device.







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







U-interface
adj. Specifies an ISDN communications device that connects directly to an ISDN telephone line. A U-interface device contains its own network terminator (NT1).







U-interface, Adj.
An ISDN communications device that connects directly to an ISDN telephone line. A U-interface device contains its own network terminator (NT1).







UDP
User Datagram Protocol







UDP Port
A 16-bit number that allows multiple processes to use User Datagram Protocol (UDP) services on the same host. A UDP address is the combination of a 32-bit IP address and a 16-bit port number. Examples of well-known UDP ports are 7 (for Echo packets), 161 (for SNMP packets), and 514 (for Syslog packets).







UDP Queue
A queue containing unprocessed User Datagram Protocol (UDP) requests.







UNI
User-Network Interface. 1) An interface point between Asynchronous Transfer Mode (ATM) end users and a private ATM switch, or between a private ATM switch and the public carrier ATM network; defined by physical and protocol specifications in ATM Forum UNI documents. 2) A similar connection in a Frame Relay network . 3) The interoperability standard adopted by the ATM Forum to define connections between users or end stations and a local switch.







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







UNIX To UNIX Copy Program (UUCP)
An application program developed in the mid 1970’s for Version 7 UNIX that allows one UNIX time sharing system to copy files to or from another UNIX time sharing system over a single link.







URL
Uniform resource locator. The address of a file (resource) accessible on the Internet. The type of resource depends on the Internet application protocol. For the World Wide Web's protocol, the Hypertext Transfer Protocol (HTTP), the resource can be an HTML page, a program such as a Java applet, or any other file supported by HTTP. The URL contains the name of the protocol required to access the resource, a domain name that identifies a specific computer on the Internet, and, if necessary, a path to the resource on the computer. The URL for Lucent Technologies, for example, is http://www.lucent.com.







UTP
Unshielded Twisted Pair







UTP cable
Unshielded Twisted Pair cable. Two paired wires with wire twisted two or more times per inch to help cancel out noise.







UUCP
UNIX-to-UNIX Copy Program. Interactive communication system for connecting two UNIX computers to send and receive data.







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







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







Unified Messaging
A platform that lets users send, receive and manage all email, voice and fax messages from any telephone, PC or information device. By linking to a consumer's e-mail account, for example, one component of unified messaging -- Lucent's Message Notifier solution -- immediately and proactively alerts users via their voice/fax mailbox that they have received e-mail.







Universal Asynchronous Receiver/Transmitter (UART )
A UART is a chip that provides a RS-232C data terminal equipment (DTE) interface to a device, enabling the unit to communicate with its attached serial devices.







Universal Time
The Greenwich Mean Time.







Unshielded Twisted Pair Cable
UTP cable consists of two wires twisted two or more times per inch in order to help cancel out noise. The entire cable has no covering. UTP cable is typically used in telephone lines for voice service, ARCnet networks, 10Base-T Ethernet networks, and particular sections of token ring networks.







Unspecified Bit Rate (UBR)
UBR is an asynchronous transfer mode (ATM) service class that handles bursty LAN traffic, as well as data that is tolerant of delays and cell loss. UBR is a best-effort service that does not specify bit-rate or traffic values, and offers no Quality of Service (QoS) guarantees.







Upstream Path
The path a call takes from the end user’s home to the carrier’s central office (CO).







User Datagram Protocol (UDP)
UDP is a transport-layer protocol that provides connectionless service without packet acknowledgment.







User-Network Interface (UNI)
The point at which users connect to the network.







 

V

V.110
A rate-adaption standard, based on fixed frames, that subdivides the ISDN channel so that it can carry one lower-speed data channel.







V.110 Terminal Adapter
A V.110 TA is a device that changes the format of asynchronous data to match the specifications of the V.110 standard for data transmission over an ISDN line.







V.120
A standard for encapsulating asynchronous data communication into synchronous ISDN data. Using standard, asynchronous-only COM ports and a V.120 Terminal Adapter (TA), two computers can communicate over an ISDN connection.







V.120 Terminal Adapter
A V.120 TA is an asynchronous device that changes the format of asynchronous data to match the specifications of the V.120 standard for data transmission over an ISDN line. A V.120 TA is also known as an ISDN modem.







V.21
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for 300-bps full-duplex modems.







V.22
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that supports a data rate of up to 1200 bps at 600 baud.







V.22bis
An extension of the V.22 standard, providing a data rate of up to 2400 bps at 600 baud.







V.23
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for 600-bps and 1200-bps full-duplex modems.







V.24
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that specifies a physical-layer interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE). V.24 is nearly identical to RS-232.







V.25
An automatic calling and answering command set for use between DTE and DCE that includes both in-band and out-of-band signaling.







V.25 bis
An automatic calling and answering command set for use between DTE and DCE which includes both in-band and out-of-band signaling.







V.25bis
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for automatic calling and answering equipment on (PSTN).







V.32
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for full-duplex modem transmission of data across phone lines at rates of up to 9600 bps, with a fallback rate of 4800 bps. A V.32 modem automatically adjusts its transmission speed based on the quality of the line.







V.32bis
An extension of the V.32 standard, providing a data rate of up to 14,400 bps or fallback to 12,000, 9600, 7200, and 4800 bps.







V.34
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for full-duplex modem transmission of data across phone lines at rates of up to 28,800 bps. A V.34 modem automatically adjusts its transmission speed based on the quality of the line.







V.34bis
An extension of the V.34 standard, providing a data rate of up to 33,600 bps. Compare with V.34.







V.35
Commonly used to describe electrical characteristics and connector characteristics for a high-speed synchronous interface between DTE and DCE. Originally V.35 described a 48 Kbps group band modem interface with electrical characteristics defined in an appendix. Although V.35 is considered obsolete and no longer published by the CCITT, its legacy lives on in the data communications world in the form of the electrical characteristics originally described in the appendix.







V.42
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) error-detection standard for high-speed modems over digital telephone lines. The V.42 standard makes use of the link access procedure, modem (LAPM).







V.42bis
An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) data-compression standard for use with V.42 technology. The V.42bis data-compression standard provides a maximum of a four-to-one data-compression ratio. Because compression algorithms are software based, overhead can cause problems in real-time environments. Most of the time, V.42bis can sense when compression is unnecessary, and so can avoid slowing the transfer of precompressed files.







V.90
A standard for data transmission over a modem at 56 kilobits per second. The V.90 standard resolves the difference between two modem technologies - x2 and K56flex. Both technologies now conform to V.90, and most previously manufactured 56Kbps modems can support V.90 via a software upgrade. See also K56flex.







VDC
Volts DC







VLAN
Virtual LAN. A group of devices on one or more LANs that communicate as if they were connected to the same wire even though they are physically located on different local area network segments. Because VLANs are configured through software rather than hardware, they are extremely flexible.







VPN
Virtual private network. A restricted network that uses public wires to connect nodes. A VPN provides a way to encapsulate, or "tunnel," private data cheaply, reliably, and securely through a public network, usually the Internet.







VSAT
Very small aperture terminal. Relatively small satellite antenna used for satellite-based point-to-mulit-point data communications applications.







VSU
Video Service Unit. See Multiband VSU.







VT-100
An ASCII character data terminal, consisting of screen and keyboard. Manufactured by Digital Equipment Corporation (DEC), the VT-100 has become an industry standard data terminal. VT-100 emulation software allows a standard PC to act as a VT-100 terminal. Videoconferencing







VTP
Virtual Terminal Protocol. An application for establishing a virtual terminal connection across a network.







Variable Bit Rate-Real Time (VBR-RT )
VBR-RT is an asynchronous transfer mode (ATM) service class that handles the packaging of special delay-sensitive applications, such as packet video, that require low cell-delay variation between endpoints.







Very High Bit Rate Digital Subscriber Line (VDSL)
VDSL is an asymmetric DSL technology that offers about eight times the performance of ADSL. The downside is that it requires a fiber-optic line from the central office (CO) to the subscriber’s neighborhood. Because infrastructure changes are required in the local loop, VDSL is considered a specialized and long-term technology.







Video Dial Tone
A network concept in which common carriers deliver video services in response to customers' dial-up commands, the same way users access the public network by dialing their phones.







Video Headend
Node on a video network where incoming program signals are converted to distribution signals and moved out onto the video distribution network for transmission to subscribers.







Video on Demand
The ability for a subscriber to an interactive TV service to select and view a specific program provided by a device such as an interactive video server.







Videoconferencing
The use of digital video transmission systems to communicate between sites using video and voice. Digital video transmission systems typically consist of camera, codec (coder-decoder), network access equipment, network, and audio system.







Virtual Bandwidth
Channel capacity calculated to allow for the over subscription of channel usage.







Virtual Channel (VC)
A communications link that carries asynchronous transfer mode (ATM) cells between two points over a shared facility. The link can be established on-demand (as a switched service), or pre-provisioned (as frame relay PVCs). The two communicating ATM entities are associated by a Virtual Path Identifier (VPI) and the Virtual Channel Identifier (VCI). All communications proceed along the same VC, preserving cell sequence and Quality of Service.







Virtual Circuit (VC)
On a frame relay, X.25 or Open Shortest Path First (OSPF) network, a VC is a bi-directional data path between two endpoints.







Virtual Circuit Manager
In each asynchronous transfer mode (ATM) node, the VC manager is the switching intelligence that builds the input port-to-output port VC mappings required for the switching device’s basic operation. The VC manager also compares the bandwidth resources required by an additional connection against the actual available resources on a link, thereby helping to prevent circuits from being created in congested areas of the network.







Virtual Paths
A bundle of virtual channels that have the same endpoint, enabling them to be manipulated as if they were a single channel.







Visitor Location Register
In cellular communications, a database that stores the information to handle calls while mobile subscribers roam outside their home areas.







VoIP
A category of hardware and software that allows people to use the Internet to make telephone calls. Currently, VoIP does not offer the same quality of telephone service as direct telephone connections. VoIP is also known as Internet telephony and Voice over the Internet.







Vocoder (Voice encoder)
Converts the analog sounds of the human voice into the zeroes and ones of digital code for computer processing.







Voice-over-IP (VoIP)
A term applied to a set of facilities for managing the delivery of voice information using the Internet Protocol (IP). Voice information is sent in digital form in discrete packets over the Internet instead of in analog form over the public switched telephone network (PSTN). A major advantage of VoIP is that it avoids the tolls charged by ordinary telephone service.







Voice-over-frame Relay (VoFR)
A term applied to a set of facilities for managing the delivery of voice information using frame relay.







Volt
The force required to produce a current of one ampere through a resistance or impedance of one ohm.








ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->T

T

T1
A digital transmission link with a capacity of 1.544 Mbit/s, used in North America. Typically channelized into 24 DS0s, each capable of carrying a single voice conversation or data stream. Uses two pairs of twisted pair wires.







T1 (T-carrier)
A digital transmission service leased from a telephone company. T1 is a 1.544 megabit channel that can handle 24 voice or data channels at 64 kilobits per second. T2 is a 6.312 megabit channel, and T3 is a 44.737 megabit channel. Because of it's high speed, many businesses lease T1 lines to link to the internet.







T1 Access Line
A 1.544 mbps T1 line that provides 24 56 kbps data channels and uses inband signaling. This type of line can contain all switched channels, all nailed-up channels, or a combination of switched and nailed-up channels. You can connect this type of line to standard voice or Switched-56 data services. Using a feature called Drop-and-Insert, the MAX can use a portion of a T1 access line for data purposes and pass the remaining portion of the line's bandwidth to a PBX for voice purposes.







T1 Channel
One of 24 channels on a T1 line.







T1 Line
A line that supports 24 64-Kbps channels, each of which can transmit and receive data or digitized voice. The line uses framing and signaling to achieve synchronous and reliable transmission. The most common configurations for T1 lines are ISDN Primary Rate Interface (T1 PRI) and unchannelized T1, including fractional T1.







T1 PRI line
A T1 line that uses 23 B channels for user data, and one 64 kbps D channel for ISDN D-channel signaling. The B channels can be all switched, all nailed up, or a combination of switched and nailed up. This type of PRI line is a standard in North America, Japan, and Korea. PRI stands for Primary Rate Interface. You can connect this type of line to standard voice, or Switched-56, Switched-64, Switched-384, Switched-1536, and MultiRate data services. Using a feature called PRI-to-TI conversion, the MAX can share the bandwidth of a T1 PRI line with a PBX.







T3
A digital transmission link with a capacity of 45 Mbps, or 28 T1 lines.







T3 Line
A digital transmission link consisting of 28 T1 lines with a total bandwidth of 44.736 Mbps.







TACACS
Terminal Access Concentrator Access Control Server. A very simple query/response protocol that enables the MAX to check a user's password, and enable or prevent access. A TACACS server supports only the basic password exchanges that PAP uses; it does not support CHAP.







TCP
Transmission Control Protocol







TCP/IP
Transmission Control Protocol/Internet Protocol. An open network standard that defines how devices from different manufacturers communicate with each other over interconnected networks. TCP/IP protocols are the foundation of the Internet.







TDM
Time Division Multiplexer (or Time Division Multiplexing) Terminal Adapter -- A device that allows analog voice and data devices to work through an ISDN connection. The terminal adapter is a protocol converter that adapts equipment not designed for ISDN, such as phones, faxes, and modems.







TE
Terminal Equipment







TEC
Thermal Electric Cooler. A device which uses the Peltier effect to heat or cool as necessary to keep the laser temperature constant.







TELENET
A public packet switched network using the CCITT X.25 protocols owned and operated by GTE.







TFTP
Trivial File Transfer Protocol. A simplified version of the File Transfer Protocol that transfers files but does not provide password protection or user directory capability.







TG
Transmitter Gain







TIA
Transimpedance amplifier







TVRO
Television, receive only. An earth station designed to handle downlink signals only.







Tagged Image File Format (TIFF)
A still graphics file format that handles monochrome, gray scale, and color images and uses a variety of compression methods. See JPEG and GIF.







Tariff
Documents filed by a regulated telephone company with a state public utility commission or the Federal Communications Commission. Document details services, equipment, and pricing publicly offered by the telephone company.







Telco
Telephone company.







Telecommunications Industries Association
The group responsible for setting telecommunications standards in the United States.







Telecommuter
A work-at-home computer user who connects to the corporate LAN backbone using remote access technologies (for example, using a modem over analog lines, ISDN Terminal Adapter (TA) or ISDN router over ISDN lines, or CSU/DSU over Switched 56 lines).







Telemedicine
A multimedia distance application in which an attending physician can consult with a remote specialist sharing test results such as X-rays and other data.







Telephony Application Programming Interface (TAPI)
From Microsoft and Intel, TAPI allows applications on client computers running Windows to access voice services on a server. TAPI lets PCs and telephone gear work together, including phone systems and PBXs. See TSAPI.







Telephony Services Application Programming Interface (TSAPI)
A telephony programming interface that links a PBX with a NetWare server so PCs and telephone gear can work together. See TAPI.







Telnet
Terminal-to-remote host protocol developed for ARPAnet. It is the TCP/IP protocol governing the exchange of character-oriented terminal data. This protocol is used to link two computers in order to provide a terminal connection to the remote machine.
Instead of dialing into the computer, you connect to it over the Internet using Telnet. When you issue a Telnet session, you connect to the Telnet host and log in. The connection enables you to work with the remote machine as though you were a terminal connected to it.







Terabit
One trillion bits.







Terminal
A computer that does not have its own processor and that must connect to a terminal server in asynchronous mode in order to use its CPU. VT100, ANSI, and TTY are all types of terminals.







Terminal Access Concentrator Access Control Server (TACAS)
A very simple query/response protocol that enables an access concentrator to check a user's password, and enable or prevent access. A TACACS server supports only the basic password exchanges that PAP uses; it does not support CHAP.







Terminal Access Controller (TAC)
A program and a piece of hardware that connects terminals to the Internet.







Terminal Adapter
A device that allows analog voice and data devices to work through an ISDN connection. The terminal adapter is a protocol converter that adapts equipment not designed for ISDN, such as phones, faxes, and modems.







Terminal Adapter (TA)
A TA is a protocol converter that adapts non-ISDN equipment (such as a phone, fax, or modem), and enables each device to work over an ISDN connection. A TA has two functions. First, it must change the format of transmitted data to match the V.120 standard for asynchronous transfer over a B channel. Second, it must provide a way of setting up and clearing calls, usually by means of Hayes AT commands. A TA is to an ISDN line what a modem is to an analog telephone line. However, some of the D-channel information does not pass through the TA, so non-ISDN equipment cannot take full advantage of ISDN facilities, such as Calling-Line ID (CLID).







Terminal Emulator
A program that makes your computer look like a terminal so that you can connect to a terminal server. Your computer acts like a terminal during the connection; all processing is taking place remotely. A terminal emulator is also called a terminal emulation program.







Terminal Server
A terminal server is a computing device to which a terminal can connect over a LAN or WAN link. A terminal communicates with the terminal server over an asynchronous serial port (typically an RS-232 port) through a modem. A terminal converts the data it receives from the terminal server into a display and does no further processing of the data. A terminal also converts the operator's keystrokes into data for transmission to the terminal server.







Terminal Server Session
An end-to-end connection between a terminal and a terminal server. Usually, the terminal server session begins when the call goes on line and ends when the call disconnects.







Thermal Electric Cooler
A device which uses the Peltier effect to heat or cool as necessary to keep the laser temperature constant.







Thick Ethernet
A term that describes a type of Ethernet cable. Thick Ethernet, or thicknet, is .4" diameter coaxial cable for Ethernet networks.







Thin Ethernet
A term that describes a type of Ethernet cable. Thin Ethernet, or thinnet, is .2" diameter coaxial cable for Ethernet networks.







Throughput
The actual speed of a network.







Time Division Multiple Access (TDMA)
Time Division Multiple Access: a multiplexing standard that divides each carrier into three time slots--with one subscriber per slot. Transmission signals are broken up into tiny packets of information--which are sent in timed bursts in the 30 megahertz range--and are reassembled at the receiving end.







Time To Live (TTL)
The hop limit counter (value=32) for IP packets.







Timeout
An event in which a device or user exceeded a configured time limit for responding to a device or process.







Token Ring
A network architecture that uses a ring topology, baseband signaling, and the token-passing media-access method. Token ring can operate at 1, 4, or 16 Mbps, and supports four-wire twisted pair or fiber-optic media.







Topology
The design of a network. Physical topology refers to the layout of the hardware. Logical topology refers to the paths that messages take to get from one node to another.







Traceroute
A superset of PING used to evaluate the hops taken from one end of a link to the other.







Traffic Contract
An asynchronous transfer mode (ATM) configuration that guarantees the delivery of a specified amount of data. While data above the traffic contract can still be delivered when network resources are available, data that exceeds the traffic contract can be delayed or lost when conditions are congested.







Traffic Shaping
In frame relay, a set of rules for defining traffic flow. The sender has a mechanism that ensures that the transmission of guaranteed packets occurs in a certain way. The network knows the kind of traffic to expect, and can monitor the behavior of the traffic. In asynchronous transfer mode (ATM), traffic shaping is a method of modifying the traffic characteristics of a stream of cells in order to achieve better network efficiency and meet all Quality of Service (QoS) objectives.







Transceiver
A device that connects a host interfaces to local area network. Ethernet transceivers contain analog electronics that apply signals to the cable and sense collisions.







Transduction
The basic concept behind voice transmission; the conversion of energy from one form into another.







Transimpedance amplifier
An electrical circuit or device that accepts a current at its input and generates a voltage at its output.







Transistor
A semiconductor device that amplifies a signal or opens and closes a circuit. In computers, it acts as a switch. Transistors and other devices -- such as resistors, capacitors and diodes -- make up logic gates. Logic gates make up circuits, and circuits make up electronic systems, such as computers. See for more info.







Transmission
Analog vs. digital transmission. Analog transmission requires more precision than a voice transmission; even if a slight error occurs during a conversation, the listener can usually compensate and understand the speaker.







Transmission Control Protocol/Internet Protocol (TCP/IP)
A protocol capable of linking different computer platforms across the Internet.







Transmitter
In fiber optic communications, a light source whose beam can be modulated and sent along an optical fiber, and the electronics that support it.







Trivial File Transfer Protocol (TFTP)
A simplified version of FTP that transfers files but does not provide password protection or user-directory capability. It is associated with the TCP/IP family of protocols. TFTP depends on the connectionless datagram deliver service, UDP.







Trunk
The communications circuit between two nodes.







Trunk Restoration
A process that reroutes the permanent virtual circuits (PVCs) on the backup trunk to the primary trunk.







Trunk Side
Trunk is a communication line between two switching systems. The term switching system typically includes equipment in a central office (telephone company) and PBXs. A tie trunk connects PBXs. Central office trunks connect a PBX to the switching system at the central office.







Trunk-side Connection
A line that extends from the telephone company’s central office (CO) to the telephone network. Typically, a trunk-side connection is high-bandwidth and all digital.







Tunneling
A way of overcoming protocol restrictions on a network by encapsulating packets that use one protocol inside packets that use a protocol supported by the network.







Twisted Pair
Relatively low-speed transmission medium consisting of two insulated wires - shielded or unshielded-in regular spiral patterns. The wires are twisted around each other to minimize interference from other twisted pairs in the cable. Twisted pair is common in telephone wiring and is increasingly common in data networks. Other high-speed forms of cable include coaxial and fiber optic cables.







Twisted-pair Cable
A cable consisting of four or more copper wires twisted together in pairs. Telephone wiring is an example of twisted-pair cable. Twisted-pair cable can be shielded or unshielded.







Two-wire Subscriber Loop
The two-wire WAN link connecting the customer premises equipment (CPE) to the carrier’s switch.