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Telos Zephyr Xstream Two-Way Radio User Manual

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USER’S MANUAL

Appendix 10 – Glossary 357

PacketSwitchingPacketSwitchednetworksaremorecommonlyassociatedwithComputers,

LocalAreaNetworks,andtheInternet.Inapacketswitchednetworktherawstreamofdatais

brokenintoindividualpieces,calledpackets.Eachpacketisroutedthroughthedatanetwork,

individually.Thisissomewhatanalogoustotakingthepagesofabookandse

ndingeachpageas

aletterthroughthepostalsystem.Thepagenumberswouldallowreassemblyofthebookno

matterwhatorderthepageswerereceivedatthefarend.Theenduserdoesnotknoworcare

thatthepacketsmaytravelavarietyofroutes.Ifagi

venpagedidnotarriveinareasonable

lengthoftime,onecouldrequestthatthispagebere‐sent.Mostpacketswitchedsystemsallow

packetstobediscardedifthenetworkcapacityisexceeded(thepostalsystemisnotsupposed

todothis).Thisisaccommodatedbythehi

gher‐levelprotocol,whichknowstorequestthata

packetbere‐sentifitdoesnotarrive.Therefore,thetypicalbehaviorofapacketswitched

networkwhenoverloadedisthatthroughputdecreases(i.e.thenetwork"slowsdown")asthe

percentageofdiscardedpacketsincreases.InstarkcontrasttoCircuitSwi

tchednetworks.See

CircuitSwitching.

PBX‐PrivateBranchExchangeAprivatelyownedswitch.Basically,aPBXisaprivate“business”

telephonesystemwhichalsointerfacestothetelephonenetwork.Insomecircles'PBX'impliesa

manualswitchboardwhereas'PABX'(PrivateAutomaticbranchexchange)impliesaPBXthat

supportsdialingbyendus

ers.ManyPBX’scannowofferISDNBRIservice,usuallyovertheS

Interface.AfewvendorsarenowofferingBRIovertheUinterfaceaswell.PRIoverDSX‐1/T1or

E1isalsoofferedinsomecases.BewaryoftheseISDNprotocolssincetheyhavenotbee

nas

welltestedastheversionsrunningon“public”switches.Theymayormaynotworkwithagiven

pieceofCPE.

PIC‐PrimaryInterexchangeCarrier(USA)Thisisyourdefault“1+”carrierusedforinterLATA

calls.InsomeareasyoumayhavetwoPICs,oneforinterLATAcalls,andoneforintraLATAlo

ng

distancecalls(inwhichcaseitstandsforPrimaryIntraexchangeCarrier).Insomeareas

intraLATAlongdistancecallsarestillhandledbyyourRBOC,inothersyounowhaveachoice.

YoumaybeabletodiscoverwhoyoucurrentPICisbydialing700555‐4141.

PMP(U

SA)AT&T“CustomPointtoMulti‐Point”CustomISDNProtocol.Notsupportedbythe

ZephyrorZephyrExpress.SeeCustomISDNandISDNProtocol.

POP‐PointOfPresenceThelocalfacilitywhereyourIECmaintainsaswitch.Thisiswhereyour

longdistancecallsgetroutedsothatyourIECcanha

ndlethem.Alsousedtodescribethelocal

accesspointofanInternetServiceProvider.

PortThisisaprettygeneralterm.Newton’sTelecomDictionary10theditiondefinesaportas

“Anentrancetooranexitfromanetwork”.Manyphoneequipmentvendorsrefertoportsas

thephysicalin

terfacebetweenaSwitchandaLineorTrunk.Productliteratureoftenrefersto

thenumberofportsonaphonesystem.Inthiscontextitreferstothenumberofphonesor

lines(orsometimesthecombination)thesystemsupports.

POT‐PlainOldTelephoneAblack,rotary‐dialdeskphone.Usuall

yaWesternElectricmodel

500set.Outdatedterm.

POTS–PlainOldTelephoneServiceRegularold‐fashionedanalogloopstartphoneservice.

PRIISDN

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