SA (Source Address)
- The address from which the message or data originated.
SA (Source MAC
Address) - A six octet value uniquely identifying an end point and
which is sent in an IEEE LAN frame header to indicate source of frame.
SAAL (Signaling ATM
Adaptation Layer) - The Signaling ATM Adaptation Layer resides between
the ATM Layer and Q.2931. Its purpose is to provide reliable transport of
Q.2931 messages between peer entities such as an ATM switch and an ATM host.
- Connection made to ground, as a protective measure, usually from the frame or
chassis of a piece of equipment.
SAP (Service Access Point)
- the point at which an entity of a layer provides services to its LM entity or
to an entity of the next higher layer.
SAR (Segmentation And
Reassembly) - the SAR accepts PDUs from the CS and divides them into
very small segments (44 bytes long). If the CS-PDU is less than 44 bytes, it is
padded to 44 with zeroes.
A two-byte header and
trailer are added to this basic segment. The header identifies the message type
(beginning, end, continuation, or single) and contains sequence numbering and
The trailer gives the
SAR-PDU payload length, exclusive of pad, and contains a CRC check to ensure
the SAR-PDU integrity. The result is a 48-byte PDU that fits into the payload
field of an ATM cell.
Satellite Downlink -
Microwave radio link from a satellite to a ground station on earth.
Satellite Office (Exchange)
- A local end office (or exchange) on a low level of the telephone network
hierarchy which is associated with another local office and which has no route
switching functions except those towards the associated higher level local
office. A satellite exchange normally has the capability to connect local
subscribers' lines terminating in it without switching through to the higher
Satellite Uplink -
Microwave link from a ground station to a satellite.
SBus - hardware
interface for add-in boards in later-version Sun 3 workstations.
Connectors or Cabling) - Designation for an Optical
Connector featuring a 2.5 mm physically contacting ferrule with a push-pull
mating design. Commonly referred to as Structured Cabling, Structured
Connectors or Stick and Click.
SC (System Controller)
- CellPath 300 System Controller; paired with the Extension Module (EM).
Connector) -Two fibers ganged side-by-side.
Defines when and in what order to service queues.
Schematic Diagram -
A functional diagram of a circuit using conventional symbols for components.
Schottky Circuit -
Circuit which takes advantage of the Schottky effect which occurs in junctions
between metals and semiconductors and results in an increase in the operating
speed of the device.
Scope - A scope
defines the level of advertisement for an address. The level is a level of a
peer group in the PNNI routing Hierarchy.
Scope - A cathode
SCP (Switch Control
Processor) - The main processor for an ASX switch.
Rectifier) - Rectifier sometimes used in central office battery
chargers which can be turned on by a control circuit.
SCR (Sustainable Cell
Rate) - parameter defined by the ATM Forum for ATM traffic
management. For VBR connections, SCR determines the long-term average cell rate
that can be transmitted.
SCSI (Small Computer Systems
Interface) - a standard for a controller bus that connects disk drives
and other devices to their controllers on a computer bus. It is typically used
in small systems.
SDLC (Synchronous Data Link
Control) - IBM's data link protocol used in SNA networks.
SDU (Service Data Unit)
- a unit of interface information whose identity is preserved from one end of a
layer connection to the other.
SEAL (Simple and Efficient
Adaptation Layer) - also called AAL 5, this ATM adaptation layer
assumes that higher layer processes will provide error recovery, thereby
simplifying the SAR portion of the adaptation layer.
Using this AAL type packs
all 48 bytes of an ATM cell information field with data. It also assumes that
only one message is crossing the UNI at a time. That is, multiple end-users at
one location cannot interleave messages on the same VC, but must queue them for
Seamless - In a LAN
environment, transparent interaction between the user and the application
accessed. The user doesn't perceive that he's on a network, i.e. his programs
run as though they were running just on his personal computer.
SECAM - (Systeme En Coleur
Avec Memoire) - Sequential and Memory Color Television - Started in
France in the late 1960s, and used by other countries with a political
The B-Y and R-Y signals
are transmitted on alternate lines modulated on an FM subcarrier. The memory is
a one line delay line in the receiver to make both color difference signals
available at the same time on all lines. Due to FM, the signal is robust in
Secondary Winding -
Output winding of a transformer. It receives power by induction from the
current flowing in the primary winding.
Segment - a single
ATM link or group of interconnected ATM links of an ATM connection.
Seismic Zone - A
geographic area designated by numerical value indicating the likelihood of
- A subfield carried in SETUP message part of ATM endpoint address Domain
specific Part (DSP) defined by ISO 10589, not used for ATM network routing,
used by ATM end systems only.
Selective Cell Discard
- A network element in an impending congested state may discard CLP=1 cells
from a CLP-significant VC.
Routines by which a phone system can alert you that there is something wrong
with the system, usually via the operator console or through one of the data
Self Test - The
capability of a system to run test programs at regular intervals to test its
own operation and to signal when failures have occurred or are about to occur
without human intervention.
Material which has a resistance to electricity somewhere between a conductor
(e.g. a copper wire) and an insulator (e.g. plastic). Silicon and Germanium are
the two most commonly used semiconductor materials. The flow of current in a
semiconductor can be changed by light, or the presence or absence of an
electric or magnetic field. < /P>
- a connection established via a service order or via network management.
Sense - To detect
the presence, absence or value of a signal.
Sensor - Detection
device which is sensitive to changes in level or state.
Serial Port - An
input/output port (plug) that transmits data out one bit at a time, in contrast
to a parallel port, which transmits data out eight bits at a time.
Service Charge -
The amount you pay each month to receive cellular service. This amount is
fixed, and you pay the same fee each month regardless of how much or how little
you use your cellular phone. It usually ranges from about $10 to $45 per month,
depending on the carrier's tariffs and the particular plan of service you
SES (Severely Errored
Seconds) - a second during which more event errors have occurred than
the SES threshold (normally 10-3).
Session Layer - Layer
5 in the OSI model that is responsible for establishing and managing sessions
between the application programs running in different nodes.
SF (Single Frequency)
- A method of in-band signaling.
SF (Super Frame) -
A term used to describe the repeating 12 D4 frame format that composes a
standard (non-ESF) T1 service.
SGMP (Simple Gateway
Management Protocol) - the predecessor to SNMP.
Shaping - The
alteration of a traffic stream on a particular connection to increase network
Shaping Descriptor -
n ordered pairs of GCRA parameters (I,L) used to define the negotiated traffic
shape of an APP connection. The traffic shape refers to the load-balancing of a
network. In this context, load-balancing means configuring the data flows to
maximize the efficiency of the network.
Shelf Life - The
useful life of components when not in use, such as those stored as spare parts
or in a warehouse awaiting shipment. Batteries tend to have the shortest shelf
life of most elecommunications components.
Shielded Cable -
Cable with metal tape shield wrapped around the insulated conductors.
Shielded Pair - Two
insulated wires in a cable wrapped with metallic braid or foil to prevent
interference and provide noise free transmission.
Short - A circuit
impairment that exists when two conductors of the same pair, which normally
make up on operating electrical circuit, are connected or touch.
Short Circuit - A
near zero resistance connection between any two wires; where two pairs are
involved, usually called a "cross." It disrupts transmission and may cause an
excessive current flow.
Shortcut - An ATM
VCC used to forward data packets in lieu of the default-routed path.
Shorted - A circuit
prevented from operating normally because two or more conductors have provided
a low resistance path, often in parallel with the device concerned, which stops
Shunt - (1) A
parallel and alternative path for current; and (2) a resistor of known value
connected in parallel with a meter to enable the meter to be used to measure
current values higher than those which would otherwise provide a full scale
deflection for the meter.
SI (Status Indicator)
- An option available on WECO coded plants for discrete or functional alarm
connections developed as CSAC features to replace the older alarm transfer
options when present (i.e. ATA, AT, ATC, etc.).
Signal - (1) An
electrical wave used to convey information; (2) an alerting signal; and (3) an
acoustic device such as a bell or a visual device such as a lamp which calls
- The amplification and/or modification of electrical signals to make them more
appropriate for transmission over a certain medium - cable, microwave, etc.
Silicon Diode -
Silicon semiconductor used as a diode rectifier. It is on all of the time,
unlike the SCR, which can be controlled.
Sine Wave - A
symmetrical time varying wave in which the amplitude is proportional to the
sine of an angle rotating at a constant rate through 360 degrees.
single mode fiber -
Type of fiber optic cable with a smaller center core than multimode fiber.
Single mode fiber can be used over relatively long distances.
Single Phase - A
circuit or device energized by a single alternating voltage; one phase of a
Varying in proportion to the sine of an angle; the shape of a sine wave.
SIR (Sustained Information
Rate) - In ATM this refers to the long-term average data transmission
rate across the User-to-Network Interface. In SMDS this refers to the committed
information rate (similar to CIR for Frame Relay Service).
SLIP (Serial Line IP)
- A protocol used to run IP over serial lines, such as telephone circuits or
RS-232 cables, interconnecting two systems.
S.M.A.R.T. ® (Sophisticated
Monitoring And Reporting Teleview) - Indicative of a family of high
quality, reliable, solid state remote monitoring systems covered by the Lorain
Products S.M.A.R.T. ® trademark. Includes the S.M.A.R.T. ® Controller/Monitor,
S.M.A.R.T. ® Monitor and S.M.A.R.T. ® Reporter.
Smart Buffers -
Refers to buffers which are able to automatically support different classes of
service while maintaining the Quality of Service (QoS) for each class.
SMDS (Switched Multimegabit
Data Service) - a high-speed, datagram-based, public data network
service expected to be widely used by telephone companies in their data
SMF (Single Mode
Fiber) - Fiber optic cable in which the signal or light propagates in
a single mode or path. Since all light follows the same path or travels the
same distance, a transmitted pulse is not dispersed and does not interfere with
adjacent pulses. SMF fibers can support longer distances and are limited mainly
by the amount of attenuation. Refer to MMF.
SMTP (Simple Mail Transfer
Protocol) - the Internet electronic mail protocol used to transfer
electronic mail between hosts.
SNA (Systems Network
Architecture) - a proprietary networking architecture used by IBM and
IBM-compatible mainframe computers.
Access Protocol) - A specially reserved variant of IEEE 802.2 encoding
SNAP indicates to look further into the packet where it will find a Type field.
SNI (Subscriber Network
Interface) - The interface between an SMDS end user’s CPE and the
network that directly serves the end user. It can be supported by either a DS1
or a DS-3 access arrangement.
SNMP (Simple Network
Management Protocol) - the Internet standard protocol for managing
nodes on an IP network.
snmpd - an SMNP
agent for a given adapter card.
Software - The
detailed instructions to operate a computer. The term was created to
differentiate instructions (i.e. the program) from the hardware.
Solder - A lead or
tin alloy which melts readily and is used in a wide variety of wire, terminal
and component connecting applications.
Soldering - Process
of joining metals by fusing them by means of a molten metal with a relatively
low melting point.
Solderless Lug -
Terminal which compresses and holds conductors by tightening a screw.
Solder Lug - Method
of terminating a heavy stranded power conductor. The conductor is forced into
one end of a short copper tube filled with molten solder. The other end of the
tube is flattened and a hole drilled through it so the lug may be bolted to a
Solid State - Any
semiconductor device that controls electrons, electric fields and magnetic
fields in a solid material and typically has no moving parts.
Solid State Circuit
- A circuit composed of solid state devices. It contains no vacuum tubes.
SONET (Synchronous Optical
Network) - a new and growing body of standards that defines all
aspects of transporting and managing digital traffic over optical facilities in
the public network.
Source - Part of
communications system which transmits information.
Source Route - A
hierarchically complete source route.
Source Traffic Descriptor
- a set of traffic parameters belonging to the ATM Traffic Descriptor used
during the connection set-up to capture the intrinsic traffic characteristics
of the connection requested by the source.
Spade Lug - A
solder lug with an open-ended two-prong spade instead of a round hole which can
be slipped under the head of a retaining screw or binding post terminal.
Spanning Tree Protocol
- provides loop-free topology in a network environment where there are
SPANS (Simple Protocol for
ATM Network Signaling) - Marconi's proprietary signaling protocol used
for establishing SVCs between Marconi equipment.
SPARC (Scalable Processor
Architecture Reduced instruction set Computer) - a powerful
workstation similar to a reduced-instruction-set-computing (RISC) workstation.
SPE (Synchronous Payload
Envelope) - the payload field plus a little overhead of a basic SONET
Specific Gravity -
Density. The ratio of the weight of a volume of a liquid or solid to the weight
of the same volume of water, usually at 4°C.
Spikes - Electrical
anomalies represented as short duration, instantaneous, very high voltage
fluctuations on an electrical service.
Split System - A
switching system that implements the functions of more than one logical node.
SPVC (Smart PVC) -
a generic term for any communications medium which is permanently provisioned
at the end points, but switched in the middle. In ATM, there are two kinds of
SPVCs: smart permanent virtual path connections (SPVPCs) and smart permanent
virtual channel connections (SPVCCs).
SS7 (Signaling System No. 7)
- The SS7 protocol has been specified by ITU-T and is a protocol for
SSCF (Service Specific
Coordination Function) - An SSCF maps the service of the SSCOP to the
needs of the specific AAL SSCF user.
SSCOP (Service Specific
Connection-Oriented Peer-to-Peer Protocol) - The SSCOP is used to
transfer variable length SDUs between users and provides for recovery of lost
or corrupt SDUs.
SSCS (Service Specific
Convergence Sublayer) - The portion of the convergence sublayer that
is dependent upon the type of traffic that is being converted.
ST (Straight Tip) -
A fiber-optic connector designed by AT&T which uses the bayonet style
coupling rather than screw-on as the SMA uses. The ST is generally considered
the eventual replacement for the SMA type connector.
Stability - Ability
to remain stable in frequency, power level, etc.
Standby Power Generator
- The engine/alternator facility present in a central office which provides AC
power when utility power is not available.
Standby Time - The
amount of time you can leave your fully charged cellular portable or
transportable phone turned on before the phone will completely discharge the
Starting Battery -
A source of reserve energy used for cranking the electric starting motor of an
engine alternator set.
State - (1) Either
of the two conditions of a bistable device, the "1" state or the "0" state; and
(2) in specification and description language, the condition in which the
action of a process is uspended and awaiting an input.
Statement of Compliance
- A detailed list which has to be submitted with most international tenders
indicating whether or not the equipment offered is fully compliant with the
requirements in the specifications.
Interference caused by natural electric disturbances in the atmosphere, in your
office, in your home. Also, containing no vacuum tubes or motor generators.
Static Route - a
route that is entered manually into the routing table.
Stationary Battery -
Battery designed to be used in a fixed location.
Station Battery - A
separate power source which provides the necessary DC power to drive a
- a technique for allowing multiple channels and paths to share the same link,
typified by the ability to give the bandwidth of a temporarily idle channel to
Connector (bayonet)) - A type of fiber optic connector.
Step-By-Step - An
electromechanical type of central office, usually referred to by the initials
Step Down - Reduce
- Transformer producing a lower output, or secondary voltage, than its input,
or primary voltage.
- Transformer producing a higher output, or secondary voltage, than its input,
or primary voltage.
STM (Synchronous Transfer
Mode) - a transport and switching method that depends on information
occurring in regular and fixed patterns with respect to a reference such as a
Storage Battery - A
battery consisting of two or more storage cells electrically connected to
produce electric energy. Common usage permits this designation to be applied
also to a single storage cell used independently.
Storage Battery Tray
- Lead or plastic tray placed under cells in a storage battery as a precaution
The technique of receiving a message, storing it until the proper outgoing line
is available, then retransmitting it, with no direct connection between
incoming and outgoing lines.
STP (Shielded Twisted Pair)
- two or more insulated wires that are twisted together and then wrapped in a
cable with metallic braid or foil to prevent interference and offer noise-free
Stray Capacitance -
Unintended capacitance between wires and components which has a significant
effect at high radio frequencies.
Stripping - Removal
of the outer sheath from a cable prior to splicing or termination.
STS (Synchronous Transport
Signal) - a SONET electrical signal rate.
Functional unit of equipment.
Sublayer - a
logical subdivision of a layer.
Substrate - The
support of an integrated circuit, either a semiconductor or an insulator.
Subsystem - A
functional unit of a system.
Summary Address -
An address prefix that tells a node how to summarize reachability information.
- A way of stopping party line phone users from hearing each other's ring by
superimposing a DC voltage over the ringing signal and using it to alert a
vacuum tube or semiconductor device in only the phone instrument for which the
ring was intended.
Super User - a
login ID that allows unlimited access to the full range of a device's
functionality, including especially the ability to reconfigure the device and
Surge Protector - A
device which plugs between the phone system and the commercial AC power outlet
to protect the system from high voltage spikes (also called surges) which might
be damaging. When a surge occurs, the surge protector sends the overload to
SVC (Switched Virtual
Circuit [or Channel]) - a channel established on demand by network
signaling, used for information transport between two locations and lasting
only for the duration of the transfer; the datacom equivalent of a dialed
SVCC (Switched Virtual
Channel Connection) - A Switched VCC is one which is established and
taken down dynamically through control signaling. A Virtual Channel Connection
(VCC) is an ATM connection where switching is performed on the VPI/VCI fields
of each cell.
SVPC (Switched Virtual Path
Connection) - A Switched Virtual Path Connection is one which is
established and taken down dynamically through control signaling. A Virtual
Path Connection (VPC) is an ATM connection where switching is performed on the
VPI field only of each cell.
Switch - Equipment
used to interconnect lines and trunks.
- A connection established via signaling.
Switching System -
A set of one or more systems that act together and appear as a single switch
for the purposes of PNNI routing.
- a connection with the same bandwidth value specified for both directions.
signals that are sourced from the same timing reference and hence are identical
Synthesized Voice -
Human speech approximated by a computer device that concatenates basic speech
parts (or phonemes) together.
System - An
organized assembly of equipment, personnel, procedures, and other facilities
designed to perform a specific function or set of functions.
System Build - The
original manufacturer system building that occurs when the order is placed by
the buyer with the vendor. The basic configuration is set up to reflect the
user's needs at that point in time. Thereafter, if any changes occur to reflect
changes in the operating environment, the manufacturer must reconfigure the
system to reflect this change, and there is usually a reprogramming charge and
delay associated with the change.