In1949,ShannonofBellTelephoneLaboratoriesintheUnitedStatesandhiscollaboratorWeaverproposedacommunicationsystemmodel,whichwaslaterwidelycitedasabasicmodelofinformationtheory..
Inthismodel,thesourcesendsoutamessage,andthemessageistransformedintoasignalthroughthetransmitter.Theprocessofsignaltransmissioninthechannelwillbeinterferedbynoise,sothereceivedsignalisactually"signal+noise".Afterthereceiver,thesignalisrestoredtoamessage,andthentransmittedtothesink.Thesignalisnotstablebecauseitmaybeinterferedbynoise,whichmaycauseadifferencebetweenthetransmittedsignalandthereceivedsignal.Inotherwords,themeaningofthemessagesentbythesourceandthemessagereceivedbythesinkmaybedifferent.Acommonreasonforcommunicationfailureisthatthesendercannotrealizethatthesentmessageandthereceivedmessagearenotalwaysthesame.
ThiscommunicationsystemmodelofShennongandWeaverisnotonlysuitableforcommunicationsystems,butcanalsobeextendedtootherinformationsystems.Theyputforwardanewfactor"noise"inthismodel,whichmeansthattheinformationisdisturbedintheprocessoftransmission.Thisshowsthatthebasicproblemoftheinformationsystemistosolvethetwoaspectsofvalidityandreliability,thatis,totransmitinformationaccuratelyandwithouterroratthemaximumrate.Theconceptof"noise"alsoremindspeopletopayattentiontotheproblemsofinterferenceandobstaclesinthecommunicationprocess.