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Glossary

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A/D Converter circuit that converts signals from analog formto digital form.ddress The numb er dialed by a calling party that identifies the party called.lso a location or

destination in a computer program.DSL A data transmission system primarily used for In ternet access, where the requirem ent is

to download large volumes of da ta from the ce ntral office.

Aliasing Th e occurrence of spurious frequencies in the o utp ut of aPCM system that were notpresent in the in pu t- d ue to foldoverof higher frequencies.M Amplitude Modulation)

variations ofa carrier sinusoid.Amplifier n elec tron ic device used to increase signal poweror amplitude.

nalogfrequency over a certain range, such s in human speechor music.

AsynchronousAttenuation The decrease in power that occurs when any signal is transmitted.

udio Frequency frequency detectable by the humanear usually between 20 and 15,000 Hz

Bandwidth The range of signal frequencies thata circuit or network will respond toor pass.Base Unit The transmitter antenna and equipment), in fixed location, and usually havinghigher power than m obile units.Binary Code A pattern of binary digits 0 and 1) used to represent information suchasinstructionsor numbers.BipolarBitof two possible alternatives.BORSCHT n acronym for the func tions that m ust be perform ed in the central office whendigital voice transmission occurs: Battery, Overvoltage, Ringing, Signaling/Supervision, Coding,Hybrid, and Test.

Byte A group of eight bits treated as a unit. Often equivalentto one alphabeticor numericcharacter.Cableby a protective sheath.CDMA Code Division Multiple Access)handsets in the U nited States.GI

may move from cellto cell.

A techniquefor sending information s patterns of amplitude

Information representedby continuous an d smoothly varying signal amplitudeor

Refers to circu itry and ope rations withou t com mon tim ing clock) signals.

Having both positive and negative polarity.n acronym for binary digit; the smallest piece of b inary inform ation; a specification of one

An assembly of one or more conductors insulated from each other and from the outside

The most common transmission method for mobile

In cellular mobile telephony, the geographic area served by one transmitter. Subscribers

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GLOSS RY

Central Office CO) T he switching equipmen t that provideslocal exchange telephone servicefor a given geographical area, designated by the first three digitsNNX or NXX) of the telephonenumber.

ChannelCircuitcommunications terminals.

Common Batteryoffice.

Companderrange of an input signal, and expandsit back to almost original formo n the output.

Critical Modemultim ode fibers.

Crossbar Switchhorizontal and vertical inp ut lines usually1 by 20), using a contact m atrixto connect any

vertical to any horizontal.CrosspointM ay be mechanical using metal contacts,or solid state using integrated circuits.Cross t a lk

CTI Computer Telephony Integration)associated data hcld o n a computer.

Current

Cutoff Frequencyor network.

D/A Converter

DataData Set

Decibel dB)dB 1 log P1/P2, where PI and P2 are the power levels in watts.Decoderby the receiver.

Demodulation

Demultiplexerthan one output line available).

Digital

Digital Subscriber Line DSL)twisted copper pairs. Such systems includeADSL, DSL, HDSL and VDSL.Distortion

DTMF Dud-Tone Multifrequency)

DTV Digital Televisiondisplay of those signals on a digitalT V set.Electromagnetic Spectrumfrequencies.

n electronic communications path, usually of4,000-Hz voice) bandwidth.An interconnected group of electronic devices, or the path connectingtwo or more

A system of supplying direct curren tfor the telephon e set from the central

n acronym for CO Mp ressor-exP AV DER , a circuit that compresses the dynamic

State in which the coreof the optical fiber is very thin com pared w ith tha t of

An electromechanical switching machine utilizing a relay mechan ism w ith

T he element tha t actually performs the switching function ina telephone system.

Undesired voice-band energy transfer from on e circuitto ano ther usually adjacent).

T he relationship between a telephone call and

Th e f low of electrical charge, measured in amperes.The frequency above whichor below which signalsare blocked by a circuit

A circuit that converts signals from digital form to analog form.

In telephone systems, any information other than hum an speech.Telephone company term for modem.

A unit of measure of relative poweror voltage, in terms of the ratio oftwo values.

Any device that modifies transmitted information to aform that can be understood

Th e processof extracting transmitted informationfrom a carrier signal.A circuit that distributes an inpu t signal to a selected ou tpu t line withmore

Information in a discreteor quantized form; not continuous.

A high-speed transmission system for carrying data over

Any difference between th e transmitted and received waveforms of the same signal

Use of two simultaneou s voiceband tones for dialing.

T he transmission and reception of digital television signals, and

T h e entire available range of sinusoidal electrical signal

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GLOSSARY

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Encoder Any device that modifies information in to a desired patternor form for a specificmethod of transmission.

ESS Electronic Switching System)

combined w ith electromechanical crosspoints, and usually with a stored-program comp uters

thecontrol element.E-TDMA Extended Time Div ision Multiple Access A comm unication system that offers amuch greater capacity than analog systems.Fxchange Area Th e territory within which te lephone service is provided withou t extra charge.

lso called the local calling areaFCC Federal Comm unications Comm ission)and monitors the domestic useof the electromagneticspectrum for communications.

Fiber O ptic Technology Th e processof transm itting infrared and visible light frequenciesthrough a low-loss glass fiber with a transmitting laseror LED.FM Frequency Modulation) A technique for sending information s patternsof frequencyvariationsof a carrier signal.Frequency Th e rate in hertz cycles per second) at which a signal patternis repeated.FSK Frequency Shift Keying A metho d of transmitting digital information that utilizes twotones; one representing a one level, the o thera zero level.Ground An electrical connection to the earthor to a comm on conductor that is connected tothe earth t some point.Ground Start A method o signaling between two machines where one machine grounds oneside of the line and the other machine detects the presence of the ground.Half-Duplex A circuit that carries information in b oth directions but only in one direction at atime.

HD SL High-Rate DSL)HDTV A high-resolution digital television combined with CD-quality Dolby digital SurroundSound.Home rea Th e geographic area in which a mobile telephone subscriberis normally located.Hybriddirection;or conversely, combines two channe ls into one.Instruction Codecomputer.Integrated Circuitintegrated structure on certain material suchs silicon.ISD N Integrated Services Digital Network)

rate ISDN-BR A) and primary rate ISDN-PRI) service.Light-emitting diode LED)multim ode glassor plastic fiber.LmesideLocal Loop

oop Sta r t

loop and the resulting current flowis detected by the switch at the other end .oss

A telephone sw itching machine using electronics, often

The U.S. govern men t agency tha t regulates

A high-ra te data transmission system usedfor ISDN-PRI.

In telephony , a circuit that divides a single transmission channel into two, onefor each

Digital informa tion that represents an instruc tion to be performed by a

A circuit whose co nnections and compon ents are fabricated into one

Data transmission system encom passing basic

A low-power device used in short-range systems using

Refers to the po rtionof the central office that mn ne cuto the local loop.Th e voiceband channel connecting the subscriber to the centraloffice.

Th e usual methodof signaling an off-hookor line seizure, where on e end closes the

Attenuationof a signal from any cause

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GLOSSARY

Message Telephone Service MTS)

Microwaves ll frequencies in the electromagnetic spectrum above billion hertz1 gigahertz).

Mobile Unit T he part of the mobile telephone system that is not fixed in its location; hence,

is not attached to the telephon e netwo rk by wires.Modulation T h e systematic changing o f the propertiesof an electronic wave, using a secondsignal, to convey the information contained in the second signal.

Multiplexing Th e divisionof a transmission facility into twoor mo re channels.

Off Hook Th e cond ition tha t indicates the active state of a customer telephone circuit. T heopposite conditio n is on-hook.

Oscillator An electronic device usedto produce repeating signals of a given frequency andamplitude.

PABX or PBX A private automatic) branch teleph one exchange system providing telephoneswitching in an officeor building.

PAC3 Personal Access Communication System)America. It uses a frequency selection algorithm to find an unused channel prior to transmissio

Parallel Data Th e transferof data simultaneou sly over twoor more wiresor transmission links.Parity

PCM Pulse Code Modulation) A comm unication systems techniqueof coding signals withbinary codes to carry the information.

PCS Personal Communication System)wireless telephone, paging, m essaging, and data service, while offering greatly improved batterylife o n the han dheld mobile units.

Period

Phase

PortableUnitnetwork by wires. Consistsof a transmitter, receiver, andperhaps a keypad.

ProgramRCC Radio Common Carrier)a telephone company.

Receiver The person or device to which information is sent over a communication link.Register A seriesof identical circuits placed side by side th at are ableto store digitalinformation.

Ringof a wire pair designated byR.Roamer A mobile telepho ne subscriber using the system outside of hisor her hom e area.Serial Data

SDH Synchronous Digital Hierarchy)transmission.

Sidetone

Simplex

SLIC Subscriber Line Interface C i t )performs someor all of the interface functions at th e central office. SeeORSCHT

T h e official nam e for long-distanceor toll service.

Digital cordless system used in Nor th

A bit that indicates whether the numb erof s in a bit string is oddor even.

A com mu nic ation system that allows all-in-one

T h e time between successive similar pointsof a repetitive sigoal.

The t ime or angle tha t a signal is delayed with respectto som e reference position.

The portion o a cordless telephone that is not electrically attachedto the

I

he sequenceof instructions stored in the comp uter memory.

A com pan y that provides mobile telephone service, but is no

Th e alerting signal to the subscriberor terminal equipment; the name for one conductor

T h e transfer of data over a single wire in a sequential pattern.A m ultiplex system th at uses opticalfiber for

T ha t po rtion o f the talkers voicethat is fed hack to hiso r her receiver.

A circuit that ca n carry information in only on e direction; for example, broadcastingIn digital transmissionof voice, the circuit tha t

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GLOSS RY

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SONET Synchronous Optical Network)transmission.State A condition ofan electron ic device especially a compu ter that is maintain ed until an

internalor external occu rrence causes change.Step-by-step SS) ystem n electromechanical telephone switching system in w hich theswitches are controlled direc tly by d igits dialed by the calling party.Subscriber Th e telephone or Internet service customer.Subscriber Loop Another term fo r local loop.Synchronous

TDM Time Division Multiplexing) A commu nication system technique that separatesinformation from channel inputs a nd places them on a carrier in specific positions in time.TDMA Time Division Multiple Acoess A commo n multiple-access method employed indigital cellular systems. TD M A is usedby he N orth American dig ital cellular system.

Tip On e conductor ofa wire pair designated byT;

usually the more positive of thetwo

Toll Center A major telephone distribution center that distributes calls from one majormetropolitan area to another.Transmission

Transmission Link Th e path over which informationflows from sender t o receiver.Transmitter The personor device that s sending information over a com munication link.Trunk A transmission channel connectingtwo witching machines.Trunkside Th e portion of the centraloffice that connects to trunks going to other switchingoffices.Voice-Grade Line A local loop or trunk having a bandpass of approximately3 to 3 000 Hz

Voltage A measureof the electrical force that causes curren tflow in a circuit.Wideband Circuit A transmission Edcility having a bandw idth greater than that of a voice-grade line.Wire Pair A local loop o ftwo wires that con nects each phone to th e central ofice.

A multiplex system tha tuses optical fiberfor

Events that are con trolled byor referred to a comm on clock.

Passing inform ation using electrom agneticenergy from one point t o another.

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