基于电话线的PC远程控制家用电器外文翻译.docx

基于电话线的PC远程控制家用电器外文翻译.docx

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基于电话线的PC远程控制家用电器外文翻译

PCREMOTECONTROLOFAPPLIANCESBYUSINGTELEPHONELINES

ABSTRACT

TheideaofHomeAutomationusingtelephonelinesandaPCwasshowninthisstudy.ThesystemwasbasedontheDualToneMultifrequencyDTMFsignalsthatcouldbesentthroughaloopofwiretoswitchon/offvariousappliancesviaaPersonalComputerPC.ThesystemhardwareandsoftwareweredesignedbasedontheTelephoneStandards.ThehardwarepartincludedtheDTMFreceiverOn/OffHookdetectorRingdetectorandanInput/OutputPCInterfacingcard.Anexampleofcontrollinganappliancewasprovidedinthestudy.ThesoftwarecontrolprogrammingwaswritteninTurboBasicandtheirflowchartsarepresentedhereforthereadersattention.

INTRODUCTION

HomeAutomationthatwasintroducedinthisstudywasimplementedbydesigningthe“SmartControlSystemthatControlsAllAppliancesRemotelybyPhone”.ThedesignwasbasedontheTelephonyStandardswhichmeantthatthesystemwasqualifiedtobeinstalledonthepublicswitchingsystems.ThesystemdesignwasutilizingtheDualToneMultifrequencyDTMFsignalsthatcouldbeproducedbythetelephoneset.Thesesignalsweresentfromtheuserendthroughtheloopwiretothedestinationend，wherethecontrolsystemwasstationed.Thesystemconsistedofthreemajorparts.ThefirstpartwastheringdetectorandDTMFreceiver.ThesecondpartwastheInput/Outputinterfaceunit.ThethirdpartwasthepersonalcomputerwhichwasprogrammedwithTurboBasicSoftwaretoperformtheonlineoperations.Blockdiagramofthesystemwasshowninfigure1.

Figure1:

SmartcontrolsystemtocontrolAppliancesremotelybyphone

BRIEFOPERATIONOFATELEPHONESET:

Asummaryofthetelephonesetoperationwasgivenhereforthereadertovisualizethesystemoperation.Blockdiagramofatelephonesetisshowninfigure2.

（a）Localloop:

Eachsubscribertelephonewasconnectedtoanexchangeofficethatcontainedtheswitchingequipment，siequipmentandbatteriesthatsuppliedthedirectcurrenttooperatethetelephone.Eachphonewasconnectedtothecentralofficethroughalocalloopoftwowirescalledawirepair.OneofthewireswascalledTfortipandtheotheronewascalledRforringwhichreferredtotheTIPandRINGpartsoftheswitchusedinmanualswitch-boards.Switchesintheexchangeofficerespondedtothedialpulsesortonesfromthetelephonetoconnectthecallingpartytothecalledparty.Whentheconnectionwasestablishedthetwotelephonescommunicatedovertransformercoupledloopsusingthecurrentsuppliedbytheexchangeofficebatteries.

（b）bInitiatingacall:

Thesituationwherethe“receiver”handsetwasliftedfromitscradlewascalledtheoff-hookcondition.Theoff-hooksignalinformedtheexchangethatsomeonewantedtomakeacall.Theexchangesentadialtonetothecallerphonetoletthecallerknowthattheexchangewasreadytoacceptatelephonenumber.Thetelephonenumberwassometimesreferredasanaddress.

（c）SendingaNumber:

Sometelephonesetssentthetelephonenumbersbydialpulseswhileotherssentitbyaudiotones.Inthisstudyaudiotonetelephonesetswereused.Thesesetshadapush-buttonkeypadwith12keys.Pressingoneofthekeyscausedanelectroniccircuitinthekeypadtogeneratetwooutputtonesthatrepresentedthenumber.ThesetonesarecalledDualToneMultifrequencyDTMFsignals.

（d）ConnectingthePhones:

Theexchangeofficehadvariousswitchesandrelaysthatautomaticallyconnectedthecallerandthecalledphones.Ifthecalledphonehandsetwasoff-hookwhentheconnectionwasattemptedabusytonewasgeneratedbytheexchangeofficeandwasreturnedtothecallerphone.Otherwisearingingsignalwassenttothecalledphonetoalertthecalledparty.Atthesametimeabacktonewasreturnedtothecallertoindicatethatthefailedphonewasringing.

（e）AnsweringtheCall:

Whenthecalledpartyremovedthehandsetinresponsetoaringthelooptothatphonewasclosedandaloopcurrentflowedthroughthecalledtelephone.Theexchangeofficethenremovedtheringingsignalandtheringtonefromthecircuit.

（f）EndingtheCall:

Intodaysmostswitchingsystemsthecallwasendedtheconnectionwasreleasedonlywhenthecallingartywenton-hook.

Figure2:

Blockdiagram

SYSTEMDESIGN：

ThesystemwasdesignedtoreceiveandrespondtotheDTMFsignals.HencethecallerpartyshoulduseatelephonesetequippedwithaDTMFkeypadforsendinganumber.TelephonesetsusingtheDTMFmethodforsendingatelephonenumberwereequippedwithapush-buttonkeypadwith12keyswhichrepresentedthenumbers0through9andthesymboland.Seefigure3.PressingoneofthekeyscausedtheDTMFgeneratortogeneratetwotonesinthevoiceband300-3000Hz.Therewasalowfrequencytoneforeachrowandahighfrequencytoneforeachcolumn.Pressingkey5forexamplegenerateda770Hztoneanda1336Hztone.Byusingthedualtonemethod12uniquecombinationswereproducedfromonlyseventoneswhenthe12positionkeypadwasused.

Figure3:

DTMFKeypadandFrequencies

Thefrequenciesandthekeypadlayouthavebeeninternationallystandardizedbutthetolerancesonindividualfrequenciesvariedindifferentcountries.TheNorthAmericanstandardswere1.5forthegeneratorandf2.0forthereceiver.ThetoneshavebeenselectedcarefullysothattheDTMFreceiverintheexchangeofficewouldnotconfusethemwiththeothertonesthatmightoccuronth6line.TheseDTMFtonesfromtheexchangeofficeweretransmittedthesameasspeechoverthetelephoneline.ThispermittedustoreceivetheDTMFtonesbyoursystemsDTMFReceiverifanynumberwaspressedonthekeypad.

（a）DTMFReceiverCircuit:

ThetaskoftheDTMFReceiverwastodetectthepresenceofavalidtonepaironatelephonelineorothertransmissionmedium.Thepresenceofavalidtonepairindicatedasingledigit.Inordertogenerateavaliddigitsequenceeachtonepairshouldbeseparatedbyavalidpause.ThefollowingtableshowedtheestablishedBellsystemstandardsforavalidtonepairandavalidpause：

Low-GroupTone：

697or770or852or941Hz

High-GroupTone：

1209or1336or1477or1633Hz

FrequencyTolerance：

for（1.5%+2Hz）

AmplitudeRange:

-24.CA<6@600Ohm

ToneDuration:

40msorlonger

PauseDuration:

40msorlonger

Figure4showedthecompletecircuitfortheDTMFreceiver.ThecircuitemployedtheRadio-Shack276-1303DTMFReceiverIC.ItwasacompleteDualToneMultifrequencyDTMFReceivercircuitdetectingaselectablegroupof12or16standarddigits.

Figure4:

DTMFReceiverampTelephoneSourcecontroller

TheblockdiagramoftheDTMFreceiverinternalstructure.Theanaloginputsignalwaspreprocessedbya60-Hzrejectfilterapreamplifierandalowpassfiltertoemphasizethesignalpart.TheoutputofthepreprocessorstagewasthensplitintotwofrequencybandseachofwhichcontainedonlyoneDTMFtonegroup.

Theoutputofeachband-splitfilterwasamplifiedandthefollowingzero-crossingdetectorconvertedthesinusoidalsignalstosquarewaves.Thesesquarewavespassedthroughtonefrequencybandpassfilterstogeneratetheindividualfrequenciesineachtonegroup.Eachbandpassfilteroutputwasdetectedbyanamplitudedetectorandfedtoatimingcircuittodeterminethedetectionvaliditywithin40ms.Thedetectoroutputwasalsofedtoanoutputdecodertodecodethetonestotheirequivalentbinarynumbers.Thetimingcircuitryproducedthecontrolpulsesforanoutputregister.ForexamplethedatastrobefromthetimingcircuitenabledthedecoderoutputstobelatchedattheregisteroutputsD1,D2,D4,D8.Theregisteroutputsbecamevalidafteratonepairhasdetectedandtheywereclearedwhenavalidpausehasarrived.TheoutputformatwasprogrammedbytheHEX/B28pin.WhenHEX/B281theoutputwashexadecimalandwhenHEX/B280theoutputwasabinarycode.Thefollowingtablesshowedthetwooutputformats.

ABCandDwereusedforextendedkeypads.TheDataValid（DV=1）pinindicatedavalidtonepairwassensedanddecodedattheoutputpinsofD1D2D4andD8.DVremainedhighuntilavalidpauseoccurred.Asshowninfigure4theinputpins9and10ofDTMFreceiverICwereconnectedtoanIsolationtransformerwhichwasusedtoisolatethetelephonelinegroundfromthedigitalground.Pin10wastiedtothedigitalgroundwhichwastheinputground.TheRingterminalofthetelephonelinewasconnectedtooneterminaloftheIsolationtransformerandtheothertransformerterminalwasconnectedtooneendofarelay.TheotherendoftherelaywasconnectedtooneterminalofacapacitorwhichalloyedACsignalstopassthrough.ThesecondterminalofthecapacitorwasconnectedtotheTipterminalofthetelephoneline.TherelayprovidedthecontrolofconnectingtheDTMFreceivertothetelephonelineviathePC.ItalsoprotectedtheDTMFreceiverfromtheringsignalsthatcoulddamageit.Theringsignalswereintherangeof40to130Vand16to60Hz.ThetypicallU.S.valueswere90Vand20Hz.Pin4wastiedtothegroundtoenablethedetectionoftonepairs.Pin2wastheHEX/B28pinanditwastiedtohightoshowthattheoutputwasinhexadecimal.Pin3wastiedtohighwhichconfiguredtheoutputstobepushpull.Pins11617and18theoutputpinsandpin14thedatavalidDVpinwereconnectedtothe1/0interfacecardviaHEXinverters.Pin7wastheICground.Itwastiedtothedigitalgroundwhichwasprovidedfromthe1/0interfacecard.Pin15CLRDVwasalsotiedtothedigitalgroundtoshowthattheDataValidDVwasclearedbyavalidpauseonly.Pin5wastheICpowersupply5whichwasprovidedfromtheI/Ointerfacecard.TheICcrystalwasconnectedbetweenthepins11and12