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Terms - S

  • S/T

    An interface between a terminal ISDN device (such as ISDN phone, ISDN fax) and NTBA equipment.

  • S0

    An interface between a terminal ISDN device (such as ISDN phone, ISDN fax) and a PBX.

  • S-bus

    A four-wire passive bus that is used at the ISDN BRI access line and provides for connecting as many as eight terminal devices.

  • SDH – Synchronous Digital Hierarchy

    This is standardised as a set of high-capacity digital transmission media, predominantly with optic digital lines, which is intended for constructing flexible, program-controlled integrated digital transmission networks.

  • SHDSL – Single pair High bit-rate DSL

    A technology using the transmission along one copper pair of wires at transmission rates varying from 160 kbit/s to 2.3 Mbit/s.

  • Signalling

    A set of signals and marks (usually electric) through which a connection between telecommunication devices is established, maintained and operated (e.g. a phone and an exchange, two exchanges, etc.). It mostly comprises a connection between two devices. It is essential to make sure that both devices use the same signalling on the same media. (For example, it is not possible to connect an ordinary phone set directly to an ISDN access line). A summary of commonly used signalling:
    K-MFC: A basic signalling for PMC connections, it uses the ab bits of the line. The selection and status of the connection is transmitted through the voice channel either by DTMF tone dialling (or by pulse dialling at the a bit), or by a multi-frequency R2 code (currently almost the only one used).
    DSS1 - ISDN: A digital subscriber EuroISDN or ETSIISDN signalling used for BRI and BRI ISDN interfaces. Currently it transmits the following services: CLIP, CLIR, COLP, COLR, SUB, DID, AOC-D, and AOC-E.
    Q sig: A digital inter-exchange ISDN signalling for connecting two telecommunication devices of the same level. It is implemented for all services pursuant to the latest ETSI specification: basic call, CLIP, CLIR, transit counters, name transmission (of the calling, called and connected parties), re-routing (immediate, when busy, if not answered), call intelligent re-routing, callback (when busy, if not answered).
    SS7 - ISDN: This has become a global standard for interconnection of telecommunications network facilities.

    The three-wire analogue DDI can be used for incoming calls only. The incoming call is signalled by the c wire followed up by the pulse dialling. Outside the exchange, the three-wire DDI is converted to a two-wire DID interface that can be processed by a PBX. The end of a call is also transmitted to both the calling and the called party.

  • SMTP – Simple Mail Transfer Protocol

    An Internet standard for the transmission of electronic mails. It applies to sending e-mails. The communication occurs at the port 25.

  • SNMP – Simple Network Management Protocol

    A network protocol based on the TCP/IP protocol that provides for monitoring and controlling of network equipment.

  • Splitter

    A device used in ADSL technology for splitting or uniting the call and data frequency bands.

  • SQL – Structured Query Language

    A programming language for entering queries and performing database modification and administration.

  • SSL – Secure socket layer

    An encrypting technology used on the Internet in order to ensure secure transactions.

  • STM-1 – Synchronous Transport Module level 1

    A synchronous transport module that specifies a structure of frames of 155.52 Mbit/s lines used in SDH networks.

  • SUB – Subaddressing

    A service that provides for several addresses for individual devices or applications within one ISDN BRI access line or standard ISDN number.

  • Subnetwork (subnet)

    A division of a network, this shares a single subnet address on an IP network with other subnets. They are also known as non-public IP addresses.

  • SVC – Switched Virtual Circuit

    A virtual connection set up temporarily between terminal nodes when communication between them is required.

  • Switch

    A network device transmitting frames on the basis of information of the second layer,
    a phone network exchange,
    a common term for mechanical or electronic equipment that sets up a connection according to the current needs and terminates it when the relation (session) is completed.




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