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Terms - D

  • Data

    This is a general term for information expressed in a digital form. This information may be voice, text, fax and video, or it may comprise a combination of these.

  • DDI – Direct Dialling In

    A possibility to access most of the PBX subscribers from an outside public telephone network through an ordinary phone number. It is usually carried out by passing the last few digits to the PBX, which processes them and rings up the subscriber specifically called. Therefore, there is no need for switchboard operator's action (switching). In order to use DDI one needs a special type of connection such as so-called analogue 3-wire DDI, PCM or ISDN connection. DDI cannot be fully realised on ordinary outside lines, as these lines require DISA.

  • Dedicated circuit

    (i) A circuit that is fully and only available to the customer for an entire term of lease. Sometimes it is just called the fixed/leased line; (ii) a signal line providing for a transmission of digital (discontinuous) signals. It may be used for transmission rates of 64 kbit/s and over.

  • Dedicated line

    A phone line that is (usually) reserved, exclusively and permanently, for a data connection of two subscribers. It is used for the Internet especially, as it is now the most used subscriber's fixed connection to the operator's backbone node.

  • Default

    A value (or device) that is pre-set (either automatically or during configuration) and offered for acceptance when options are prompted. Default values are most often used for dialogue panels or communication dialogues when the user is to set a number of values or answer a number of questions. Default values help the user to limit the number of required entries and get oriented in the dialogue. Default file extensions that comprise a sort of unwritten standard for file creation and naming are quite often used. A default device may be a peripheral unit (such as a plotter, printer, or modem) that is offered automatically when a communication with this equipment is attempted. Programs usually have an option to return their configurations back to their default settings, i.e. back to a certain starting point.

  • D-channel – data channel

    Data channel on ISDN networks with a transmission rate of 16 kbit/s (BRI) or 64 kbit/s (PRI) which is usually used to transmit signalling with respect to the ISDN call. It cannot be used for data transmission on GTS Novera's network.

  • Dial backup

    A backup of a fixed communication line through a connection set up on a switched network.

  • Dial-up

    An access to a telephone network through a modem that requires a manual or automatic connection.

  • DISA

    An alternate form for achieving direct dialling in systems connected by standard analogue lines. The calling party dials an ordinary telephone number and upon a prompt it switches to tone dialling and dials the extension number to which it wants to be connected. If the connection fails the call is usually routed to a switchboard operator.

  • DLCI – Data Link Control Identifier

    A parameter that determines a PVC (Permanent Virtual Circuit) or SVC (Switched Virtual Circuit) on Frame Relay networks.

  • Domain name

    A denomination of the “class” of computers connected to the Internet that are common geographically and organisationally e.g. all computers within the .cz domain are located in the Czech Republic, while comprise computers administrated by the company Computer Press. The names of main domains (based on geography) have already been allocated. The basic domain names are allocated by an independent organisation.

  • DSL – Digital Subscriber Line

    A technology providing for broadband transmissions to short distances through standard copper wires. Four different technologies are used: ADSL, HDSL, SHDSL and VDSL.

  • DSLAM – Digital Subscriber Line Access Multiplexer

    A device providing for multiplexing of transmissions made by the DSL technology through ordinary copper wires.

  • DSS1 – Digital Signalling System no. 1

    A subscriber signalling used on ISDN networks.

  • DSS1 - ISDN

    EuroISDN or ETSI ISDN signalling is used for both PRI and BRI ISDN interfaces. The following services are currently in use: CLIP, CLIR, COLP, COLR, SUB, DID, AOC-D and AOC-E.

  • DTMF – Dial Tone Multi-Frequency

    This is used for transmission of individual digits dialled on analogue connections. The digit dialled is presented as a combination of two exact-frequency tones sounding simultaneously. The tone dialling is fast (one digit < 0.1 second) and reliable. It can be transmitted through a connection that has already been established and use it to control remote equipment. Pulse dialling is older.

  • DWDM – Dense Wavelength Division Multiplexing

    A technology for broadband transmissions along an optic fibre. In contrast to methods that have so far been used to accelerate transmission through an increase in frequency of data transmitted, the DWDM solves this acceleration problem by splitting the information spectrally. In other words it multiplexes different frequencies into one beam which is split at the other end. The way that rainbows and optical prisms split light into the different wavelengths exemplifies the principle involved.




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