文献翻译基于电话线的PC远程控制家用电器.docx

文献翻译基于电话线的PC远程控制家用电器.docx

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文献翻译基于电话线的PC远程控制家用电器

附录

附录A

PCREMOTECONTROLOFAPPLIANCESBYUSING

TELEPHONELINES

ABSTRACT

TheideaofHomeAutomationusingtelephonelinesandaPCwasshowninthisstudy.ThesystemwasbasedontheDualToneMultifrequency（DTMF）signalsthatcouldbesentthroughaloopofwiretoswitchon/offvatiousappliancesviaaPersonalComputer（PC）.ThesystemhardwareandsoftwareweredesignedbasedontheTelephoneStandards.ThehardwarepartincludetheDTMFreceiveron/offHookdetector,RingdetectorandanInput/OutputPCInterfacingcard.Anexampleofcontrollinganappliancewasprovidedinthestudy.ThesoftwarecontrolprogrammingwaswritteninTurboBasicandtheirflowchartsarepresentedhereforthereader’sattention.

INTRODUCTION

HomeAutomationthatwasintroducedinthisstudywasimplementedbydesigningthe“SmartControlSystemthatControlsAllAppliancesRemotelybyphone”.ThedesignwasbasedontheTelephoneStandardswhichmeantthatthesystemwasqualifiedtobeinstalledonthepublicswitchingsystem.ThesystemdesignwasutilizingtheDualToneMultifrequency（DTMF）signalsthatcouldbeproducedbythetelephoneset.Thesesignalsweresentfromtheuserendthroughtheloopwiretothedestinationend,wherethecontrolsystemwasstationed.Thesystemconsistedofthreemajorparts.ThefirstpartwastheringdetectorandDTMFreceiver.ThesecondpartwastheInput/Outputinterfaceunit.ThethirdpartwasthepersonalcomputerwhichwasprogrammedwithTurboBasicSoftwaretoperfomtheonlineoperations.BlockdiagramofsystemwasshowninfigureA.1

FigureA.1SmartcontrolsystemtocontrolAppliancesremotelybyphone

BRIEFOPERATIONOFATELEPHONESET

Asummaryofthetelephonesetoperationwasgivenhereforthereadertovisualizethesystemoperation.

（a）Localloop:

Eachsubscribertelephonewasconnectedtoanexchangeofficethatcontainedtheswitchingequipment,signalingequipmentandbatteriesthatsuppliedthedirectcurrenttooperatethetelephone.Eachphonewasconnectedtothecentralofficethroughalocalloopoftwowirescalledawirepair.OneofthewireswascalledT（fortip）andtheotheronewascalledR（forring）whichwasrefferedtotheTIPandRINGpartsoftheswitchusedinmanualswitch-boards.Switchesintheexchangeofficerespondedtothecalledparty.Whentheconnectionwasestablished,thetwotelephonecommunicatedovertransformercoupledloopsusingthecurrentsuppliedbytheexchangeofficebatteries.

（b）Initiatingacall:

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

（c）Sendinganumber:

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

（d）ConnectingthePhones:

Theexchangeofficehadvariousswitchesandrelaysthatautomaticallyconnectedthecallerandthecalledphones.Ifthecalledphonehandsetwasoff-hookwhentheconnectionwasattempted,abusytonewasgeneratedbytheexchangeofficeandwasretunedtothecallerphone.Otherwise,aringingsignalwassenttothecalledphonetoalertthecalledparty.Atthesametime,aringbacktonereturnedtothecallertoindicatethatthefailedphonewasringing.

（e）AnsweringtheCall:

Whenthecalledpartyremovedthehandsetinresponsetoaring,thelooptothatphonewasclosedandaloopcurrentflowedthroughthecalltelephone.Theexchangeofficethenremovedtheringingsignalandtheringbacktonefromthecircuit.

（f）EndingtheCall:

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

SYSTEMDESIGN

ThesystemwasdesignedtoreceiveandrespondtotheDTMFsignals.Hence,thecallerpartyshoulduseatelephonesetequippedwithaDTMFkeypadforsendinganumber.Telephonesets,usingtheDTMFmethodforsendingatelephonenumbe,wereequippedwithapush-buttonkeypadwith12keyswhichrepresentedthenumbersthrough0to9andthesymbol*and#.Seefigure3.PressingoneofthekeyscausedtheDTMFgeneratortogeneratetwotonesinthevoiceband（300-3,000Hz）.Therewasalowfrequencytoneforeachrowandahighfrequencytoneforeachcolumn.Pressingkey5,forexample,generateda770Hztoneanda1,336Hztone.Byusingthedualtonemethod,12uniquecombinationswereproducedfromonlyseventoneswhenthe12positionkeypadwasused.

FigureA.3:

DTMFKeypadandFrequencies

Keypad

HighFrequency（Hz）

1209

1336

1477

1633

LowFrequency

（Hz）

697

1

2

3

A

770

4

5

6

B

852

7

8

9

C

941

*

0

#

D

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

（a）DTMFReceiverCircuit:

ThetaskoftheDTMFReceiverwastodetectthepresenceofavalidtonepaironatelephonelineorothertransmissionmedium.Thepresenceofavalidtorpairindicatedasingledialleddigit.Inordertogenerateavaliddigitsequence,eachtonepairshouldbeseparatedbyavalidpause.ThefollowingtableshowedtheestablishedBellsystemstandardsforavalidtonepairandavalidpause:

Low-GroupTone:

697or770or852or941Hz

High-GroupTone:

1209or1336or1477or1633Hz

FrequencyTolerance:

for（1.5%+2Hz）

AmplitudeRange:

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

ToneDuration:

40msorlonger

PauseDuration:

40msorlonger

Figure2showedthecompletecircuitfortheDTMFreceiver.ThecircuitemployedtheRadio-Shack（276-1303）DTMFReceiverTC.TtwasacompleteDualToneMultifrequency（DTMF）Receivercircuitdetectingaselectablegroupof12or16standarddigits.

FigureA.2DTMFReceiver&TelephoneSourcecontroller

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

Theoutputofeachband-splitfilterwasamplifiedandthefollowingzero-crossingdetectorconvertedthesinusoidalsignalstosquarewaves.Thesesquarewaves,passedthroughtonefrequencybandpassfilterstogeneratetheindividualfrequenciesineachtonegroup.Eachbandpassfilteroutputwasdetectedbyanamplitudedetectorandfedtoatimingcircuittodeterminethedetectionvaliditywithin40ms.Thedetectoroutputwasalsofedtoanoutputdecodertodecodethetonestotheirequivalentbinarynumbers.Thetimingcircuitryproducedthecontrolpulses,foranoutputregister.Forexample,thedatastrobefromthetimingcircuitenabledthedecoderoutputstobelatchedattheregisteroutputsDl.D2.D4.D8.Theregisteroutputsbecamevalidafteratonepairhasdetectedandtheywereclearedwhenavalidpausehasarrived.TheoutputformatwasprogrammedbytheHEX/B28pin.WhenHEXB28=1,theoutputwashexadecimalandwhenHEX.B28-0.theoutputwasabinarycode.Thefollowingtablesshowedthetwooutputformats.

A.B,CandDwereusedforextendedkeypads.TheDataValid（DV=l）pinindicatedavalidtonepairwassensedanddecodedattheoutputpinsofDl,D2,D4andD8.DVremainedhighuntilavalidpauseoccurred.Asshowninfigure4.theinputpins9and10ofDTMFreceiverICwereconnectedtoanIsolationtransformerwhichwasusedtoisolatethetelephonelinegroundfromthedigitalground.Pin10wastiedtothedigitalground,whichwastheinputground.TheRingterminalofthetelephonelinewasconnectedtooneterminaloftheIsolationtransformerandtheothertransformerterminalwasconnectedtooneendofarelay.TheotherendoftherelaywasconnectedtooneterminalofacapacitorwhichalloyedACsignalstopassthrough.ThesecondterminalofthecapacitorwasconnectedtotheTipterminalofthetelephoneline.TherelayprovidedthecontrolofconnectingtheDTMFreceivertothetelephonelineviathePC.ItalsoprotectedtheDTMFreceiverfromtheringsignalsthatcoulddamageit.Theringsignalswereintherangeof40to130Vrmsand16to60Hz.Thetypical1U.S.valueswere90Vrmsand20Hz.Pin4wastiedtothegroundtoenablethedetectionoftonepairs.Pin2wastheHEX/B28pinanditwastiedtohightoshow-thattheoutputwasinhexadecimal.Pin3wastiedtohigh,whichconfiguredtheoutputstohepushpull.Pins1,16,17and18,theoutputpinsandpin14,thedatavalid（DV）pinwereconnectedtothe1/0interfacecardviaHEXinverters.Pin7wastheICground.Itwastiedtothedigitalgroundwhichwasprovidedfromthe1/0interfacecard.Pin15（CLRDV）wasalsotiedtothedigitalgroundtoshowthattheDataValid（DV）wasclearedbyavalidpauseonly.Pin5wastheICpowersupply（+5）whichwasprovidedfromtheI/Ointerfacecard.TheICcrystalwasconne