外文翻译基于电话线的PC远程控制家用电器.docx

外文翻译基于电话线的PC远程控制家用电器.docx

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外文翻译基于电话线的PC远程控制家用电器

PCREMOTECONTROLOFAPPLIANCESBYUSINGTELEPHONELINES

ABSTRACT

TheideaofHomeAutomationusingtelephonelinesandaPCwasshowninthisstudy.ThesystemwasbasedontheDualToneMultifrequency（DTMF）signalsthatcouldbesentthroughaloopofwiretoswitchon/offvariousappliancesviaaPersonalComputer（PC）.ThesystemhardwareandsoftwareweredesignedbasedontheTelephoneStandards.ThehardwarepartincludedtheDTMFreceiverOn/OffHookdetector,RingdetectorandanInput/OutputPCInterfacingcard.Anexampleofcontrollinganappliancewasprovidedinthestudy.ThesoftwarecontrolprogrammingwaswritteninTurboBasicandtheirflowchartsarepresentedhereforthereader'sattention.

INTRODUCTION

HomeAutomationthatwasintroducedinthisstudywasimplementedbydesigningthe"SmartControlSystemthatControlsAllAppliancesRemotelybyPhone".ThedesignwasbasedontheTelephonyStandardswhichmeantthatthesystemwasqualifiedtobeinstalledonthepublicswitchingsystems.ThesystemdesignwasutilizingtheDualToneMultifrequency（DTMF）signalsthatcouldbeproducedbythetelephoneset.Thesesignalsweresentfromtheuserendthroughtheloopwiretothedestinationend,wherethecontrolsystemwasstationed.Thesystemconsistedofthreemajorparts.ThefirstpartwastheringdetectorandDTMFreceiver.ThesecondpartwastheInput/Outputinterfaceunit.ThethirdpartwasthepersonalcomputerwhichwasprogrammedwithTurboBasicSoftwaretoperformtheonlineoperations.Blockdiagramofthesystemwasshowninfigure1.

Figure1:

SmartcontrolsystemtocontrolAppliancesremotelybyphone

BRIEFOPERATIONOFATELEPHONESET:

Asummaryofthetelephonesetoperationwasgivenhereforthereadertovisualizethesystemoperation.Blockdiagramofatelephonesetisshowninfigure2.

（a）Localloop:

Eachsubscribertelephonewasconnectedtoanexchangeofficethatcontainedtheswitchingequipment,signallingequipmentandbatteriesthatsuppliedthedirectcurrenttooperatethetelephone.Eachphonewasconnectedtothecentralofficethroughalocalloopoftwowirescalledawirepair.OneofthewireswascalledT（fortip）andtheotheronewascalledR（forring）whichreferredtotheTIPandRINGpartsoftheswitchusedinmanualswitch-boards.Switchesintheexchangeofficerespondedtothedialpulsesortonesfromthetelephonetoconnectthecallingpartytothecalledparty.Whentheconnectionwasestablished,thetwotelephonescommunicatedovertransformercoupledloopsusingthecurrentsuppliedbytheexchangeofficebatteries.

（b）Initiatingacall:

Thesituationwherethe"receiver"handsetwasliftedfromitscradlewascalledtheoff-hookcondition.Theoff-hooksignalinformedtheexchangethatsomeonewantedtomakeacall.Theexchangesentadialtonetothecallerphonetoletthecallerknowthattheexchangewasreadytoacceptatelephonenumber.（Thetelephonenumberwassometimesreferredasanaddress.）

（c）SendingaNumber:

Sometelephonesetssentthetelephonenumbersbydialpulseswhileotherssentitbyaudiotones.Inthisstudy,audiotonetelephonesetswereused.Thesesetshadapush-buttonkeypadwith12keys.Pressingoneofthekeyscausedanelectroniccircuitinthekeypadtogeneratetwooutputtonesthatrepresentedthenumber.ThesetonesarecalledDualToneMultifrequency（DTMF）signals.

（d）ConnectingthePhones:

Theexchangeofficehadvariousswitchesandrelaysthatautomaticallyconnectedthecallerandthecalledphones.Ifthecalledphonehandsetwasoff-hookwhentheconnectionwasattempted,abusytonewasgeneratedbytheexchangeofficeandwasreturnedtothecallerphone.Otherwise,aringingsignalwassenttothecalledphonetoalertthecalledparty.Atthesametime,aringbacktonewasreturnedtothecallertoindicatethatthefailedphonewasringing.

e）AnsweringtheCall:

Whenthecalledpartyremovedthehandsetinresponsetoaring,thelooptothatphonewasclosedandaloopcurrentflowedthroughthecalledtelephone.Theexchangeofficethenremovedtheringingsignalandtheringbacktonefromthecircuit.

f）EndingtheCall:

Intoday'smostswitchingsystems,thecallwasended,theconnectionwasreleased,onlywhenthecallingartywenton-hook.

Figure2:

Blockdiagram

SYSTEMDESIGN：

ThesystemwasdesignedtoreceiveandrespondtotheDTMFsignals.Hence,thecallerpartyshoulduseatelephonesetequippedwithaDTMFkeypadforsendinganumber.Telephonesets,usingtheDTMFmethod forsendingatelephonenumber,wereequippedwithapush-buttonkeypadwith12keyswhichrepresentedthenumbers0through9andthesymbol*and#.Seefigure3.PressingoneofthekeyscausedtheDTMFgeneratortogeneratetwotonesinthevoiceband（300-3,000Hz）.Therewasalowfrequencytoneforeachrowandahighfrequencytoneforeachcolumn.Pressingkey5,forexample,generateda770Hztoneanda1,336Hztone.Byusingthedualtonemethod,12uniquecombinationswereproducedfromonlyseventoneswhenthe12positionkeypadwasused.

Figure3:

DTMFKeypadandFrequencies

Thefrequenciesandthekeypadlayouthavebeeninternationallystandardized,butthetolerancesonindividualfrequenciesvariedindifferentcountries.TheNorthAmericanstandardswere*1.5%forthegeneratorandf2.0%forthereceiver.ThetoneshavebeenselectedcarefullysothattheDTMFreceiverintheexchangeofficewouldnotconfusethemwiththeothertonesthatmightoccuronth6line.TheseDTMFtonesfromtheexchangeofficeweretransmittedthesameasspeechoverthetelephoneline.ThispermittedustoreceivetheDTMFtonesbyoursystem'sDTMFReceiverifanynumberwaspressedonthekeypad.

a）DTMFReceiverCircuit:

ThetaskoftheDTMFReceiverwastodetectthepresenceofavalidtonepaironatelephonelineorothertransmissionmedium.Thepresenceofavalidtonepairindicatedasingledialleddigit.Inordertogenerateavaliddigitsequence,eachtonepairshouldbeseparatedbyavalidpause.ThefollowingtableshowedtheestablishedBellsystemstandardsforavalidtonepairandavalidpause：

Low-GroupTone：

697or770or852or941Hz

High-GroupTone：

1209or1336or1477or1633Hz

FrequencyTolerance：

for（1.5%+2Hz）

AmplitudeRange:

-24dBm.CA<+6dBm@600Ohm

ToneDuration:

40msorlonger

PauseDuration:

40msorlonger

Figure4showedthecompletecircuitfortheDTMFreceiver.ThecircuitemployedtheRadio-Shack（276-1303）DTMFReceiverIC.ItwasacompleteDualToneMultifrequency（DTMF）Receivercircuitdetectingaselectablegroupof12or16standarddigits.

Figure4:

DTMFReceiver&TelephoneSourcecontroller

TheblockdiagramoftheDTMFreceiverinternalstructure.Theanaloginputsignalwaspreprocessedbya60-Hzrejectfilter,apreamplifierandalowpassfiltertoemphasizethesignalpart.Theoutputofthepreprocessorstagewasthensplitintotwofrequencybands,eachofwhichcontainedonlyoneDTMFtonegroup.

Theoutputofeachband-splitfilterwasamplifiedandthefollowingzero-crossingdetectorconvertedthesinusoidalsignalstosquarewaves.Thesesquarewaves,passedthroughtonefrequencybandpassfilterstogeneratetheindividualfrequenciesineachtonegroup.Eachbandpassfilteroutputwasdetectedbyanamplitudedetectorandfedtoatimingcircuittodeterminethedetectionvaliditywithin40ms.Thedetectoroutputwasalsofedtoanoutputdecodertodecodethetonestotheirequivalentbinarynumbers.Thetimingcircuitryproducedthecontrolpulses,foranoutputregister.Forexample,thedatastrobefromthetimingcircuitenabledthedecoderoutputstobelatchedattheregisteroutputsD1,D2,D4,D8.Theregisteroutputsbecamevalidafteratonepairhasdetectedandtheywereclearedwhenavalidpausehasarrived.TheoutputformatwasprogrammedbytheHEX/B28pin.WhenHEX/B28=1,theoutputwashexadecimalandwhenHEX/B28=0,theoutputwasabinarycode.Thefollowingtablesshowedthetwooutputformats.

A,B,CandDwereusedforextendedkeypads.TheDataValid（DV=l）pinindicatedavalidtonepairwassensedanddecodedattheoutputpinsofD1,D2,D4andD8.DVremainedhighuntilavalidpauseoccurred.Asshowninfigure4,theinputpins9and10ofDTMFreceiverICwereconnectedtoanIsolationtransformerwhichwasusedtoisolatethetelephonelinegroundfromthedigitalground.Pin10wastiedtothedigitalground,whichwastheinputground.TheRingterminalofthetelephonelinewasconnectedtooneterminaloftheIsolationtransformerandtheothertransformerterminalwasconnectedtooneendofarelay.TheotherendoftherelaywasconnectedtooneterminalofacapacitorwhichalloyedACsignalstopassthrough.ThesecondterminalofthecapacitorwasconnectedtotheTipterminalofthetelephoneline.TherelayprovidedthecontrolofconnectingtheDTMFreceivertothetelephonelineviathePC.ItalsoprotectedtheDTMFreceiverfromtheringsignalsthatcoulddamageit.Theringsignalswereintherangeof40to130Vrmsand16to60Hz.ThetypicallU.S.valueswere90Vrmsand20Hz.Pin4wastiedtothegroundtoenablethedetectionoftonepairs.Pin2wastheHEX/B28pinanditwastiedtohightoshowthattheoutputwasinhexadecimal.Pin3wastiedtohigh,whichconfiguredtheoutputstobepushpull.Pins1,16,17and18,theoutputpinsandpin14,thedatavalid（DV）pinwereconnectedtothe1/0interfacecardviaHEXinverters.Pin7wastheICground.Itwastiedtothedigitalgroundwhichwasprovidedfromthe1/0interfacecard.Pin15（CLRDV）wasalsotiedtothedigitalgroundtoshowthattheDataValid（DV）wasclearedbyavalidpauseonly.Pin5wastheICpow