Glossary - S



Survivable adaptable fiber-optic embedded network.


Synchronous digital hierarchy.


Software defined network.


Symmetric Digital Subscriber Line is one of the family of DSL services. However, unlike ADSL, it actually offers the exact same data rate speeds of around 2Mbit/s both up and downstream. SDSL is better suited to business customers as opposed to residential customers.

Select Services

Select Services are a set of supplementary services that include call barring and callwaiting, and also ringback etc.). They are provided by BT ata rates that are set out in the retail list that BT provide.

Selective Call Barring

This is the programming of a Public Switched Network access line in a form that enables outgoing calls to a set group of related numbers (for example those at a special charge rate). However, mobile or international services cannot be made.


A server is equipment that exists in a network that makes available file, printing, database, facsimile, communications or any other services to client stations/terminals that have access to the network. A server that permits client terminal/station access to an external communications network and/or an information system, is known as a gateway.

Service Order (SO)

A service order exists as a record that describes a customers request to establish, terminate or change a service. This service order would contain all the necessary information that is required in order to fully meet a customer's needs.

Service provider

This provides to third parties, electronic communications services. It does so whether it is over its own network or not.


Single frequency.

Shared loop

This is usually usually a loop comprised by two copper wires. It is the access network connection that exists between the customer’s premises and there local PSTN exchange. This loop has two operators on it that provide the services. The first of the operators will be employing the portion of the loop that exists at lower frequencies(this is the voice telephony) and the second operator will use the higher-frequencies in order to provide the high-speed data services.


A signal is a time-dependent value that is attached to a propagating phenomenon (energy related)that is used to convey information. An example of a signal could be a soulnd or audio signal whereby the data is characterized by its pitch or loudness.


Signaling relates to the process of exchanging and generating information between the components of a telecommunications system. This exists in order to establish, release or monitor connections (call handling functions) and also to control related system and network operations (other functions).


Subscriber Identity Module.

Simple Network Management Protocol (SNMP)

SNMP exists as the application protocol that offers network management and service within the Internet suite of protocols. It is a structure for transmitting information and formatting messages between reporting devices (agents) and also data collection programs. It was developed jointly by the Department of Defense, by industry and also the academic community. It was part of the TCP/IP protocol suite; this was ratified as an Internet standard in the Request for (Comment (RFC) 1098.


Simple network management protocol. Please see Simple Network Management Protocol (SNMP).


Synchronous optical network.

Special Services

Special services include a variety of LEC and IXC non-switched, switched, or even a special rate services. These are either separate from the public telephone service or may contribute to certain aspects of it. There are many examples, and these may include PBX tie trunks or foreign exchange (FX) and/or private line services.It is worth noting that these services are very important to business telecommunication planners/users.

Speed Dial

A simple feature on PBX phones that allows users to dial pre-programmed numbers by the simple act of pressing one button (or maybe entering a two or even three digit code).


Switched service network.


Signaling system.


Synchronous transfer mode.


STP, or Signalling Transfer Point, is a facility where C7 signalling messages are able to be passed between exchanges that did not require a discrete circuit to exist between them.


Switching refers to a process of connecting the appropriate trunks and/or lines in order to form a desired communications path that exists between two station sets, or it is also known as two arbitrary points in a telecommunications network. Within this is included all kinds of related functions, for example signaling or monitoring the status of circuits. Or may even include the translating of an address to routing instructions, or alternate routing, it may also inlcude detecting and recording troubles or testing circuits for busy conditions.

Switching Systems

Switching systems exist as interconnect transmission facilities that operate at various network locations and then route traffic through a network.

Synchronous Digital Hierarchy (SDH)

This is a method of digital transmission. It exists where the data is packed in containers. These are then synchronised in time, thus enabling relatively simple multiplexing and also demultiplexing at the receiving and transmitting ends.

Systems Network Architecture (SNA)

SNA is IBM's proper description of logical structure, protocals, formats, and operational sequences. It is used for the transmission of information units and also controlling network configuration and operation.


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