Thisapplicationnotedescribeshowtoconnecta
PICmicromicrocontrollerdevicetoastandardanalog
telephonelineinordertosendandreceivesingleand
multiplefrequencysignalsthroughmodulationand
demodulation(i.e.,MODEM).Althoughtherearemany
differentelementswithinamodemsystem,weareonly
concernedherewiththelineconnection.AN854ConnectingaPICmicroMicrocontrollertoaStandardAnalogTelephoneLineFigure1showshowtheringandtiplinesrunintotheAuthor:DavidHedleyprimaryofatransformer.ThehookswitchonthelineMicrochipTechnologyInc.sideofthetransformerisnotshownbutcanbeimple-mentedwithopto-couplers,relaysorswitches.Whena
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