【正文】 0。geometry.AccesscontrolsystemponentsAnaccesscontrolpoint,whichcanbeadoor,turnstile,parkinggate,elevator,orotherphysicalbarrierwheregrantingaccesscanbeelectronicallycontrolled.Typicallytheaccesspointisadoor.Anelectronicaccesscontroldoorcancontainseveralelements.Atitsmostbasicthereisastandaloneelectriclock.Thelockisunlockedbyanoperatorwithaswitch.Toautomatethis,operatorinterventionisreplacedbyareader.Thereadercouldbeakeypadwhereacodeisentered,itcouldbeacardreader,oritcouldbeabiometricreader.Readersdonotusuallymakeanaccessdecisionbutsendacardnumbertoanaccesscontrolpanelthatverifiesthenumberagainstanaccesslist.Tomonitorthedoorpositionamagneticdoorswitchisused.Inconceptthedoorswitchisnotunlikethoseonrefrigeratorsorcardoors.Generallyonlyentryiscontrolledandexitisuncontrolled.Incaseswhereexitisalsocontrolledasecondreaderisusedontheoppositesideofthedoor.Incaseswhereexitisnotcontrolled,freeexit,adevicecalledarequesttoexit(RTE)isused.Requesttoexitdevicescanbeapushbuttonoramotiondetector.Whenthebuttonispushedorthemotiondetectordetectsmotionatthedoor,thedooralarmistemporarilyignoredwhilethedoorisopened.Exitingadoorwithouthavingtoelectricallyunlockthedooriscalledmechanicalfreeegress.Thisisanimportantsafetyfeature.Incaseswherethelockmustbeelectricallyunlockedonexit,therequesttoexitdevicealsounlocksthedoor.AccesscontroltopologyAccesscontroldecisionsaremadebyparingthecredentialtoanaccesscontrollist.Thislookupcanbedonebyahostorserver,byanaccesscontrolpanel,orbyareader.Thedevelopmentofaccesscontrolsystemshasseenasteadypushofthelookupoutfromacentralhosttotheedgeofthesystem,orthereader.Thepredominatetopologycirca2009ishubandspokewithacontrolpanelasthehubandthereadersasthespokes.Thelookupandcontrolfunctionsarebythecontrolpanel.Thespokesmunicatethroughaserialconnection。usuallyRS485.Somemanufacturesarepushingthedecisionmakingtotheedgebyplacingacontrolleratthedoor.ThecontrollersareIPenabledandconnecttoahostanddatabaseusingstandardnetworks.TypesofreadersAccesscontrolreadersmaybeclassifiedbyfunctionstheyareabletoperform:(1) Basic(nonintelligent)readers:simplyreadcardnumberorPINandforwardittoacontrolpanel.Incaseofbiometricidentification,suchreadersoutputIDnumberofauser.TypicallyWiegandprotocolisusedfortransmittingdatatothecontrolpanel,butotheroptionssuchasRS232,RS485andClock/Dataarenotunmon.Thisisthemostpopulartypeofaccesscontrolreaders.ExamplesofsuchreadersareRFTinybyRFLOGICS,ProxPointbyHID,andP300byFarpointeData.(2) Semiintelligentreaders:haveallinputsandoutputsnecessarytocontroldoorhardware(lock,doorcontact,exitbutton),butdonotmakeanyaccessdecisions.WhenauserpresentsacardorentersPIN,thereadersendsinformationtothemaincontrollerandwaitsforitsresponse.Iftheconnectiontothemaincontrollerisinterrupted,suchreadersstopworkingorfunctioninadegradedmode.UsuallysemiintelligentreadersareconnectedtoacontrolpanelviaanRS485bus.ExamplesofsuchreadersareInfoProxLiteIPL200byCEMSystemsandAP510byApollo.(3) Intelligentreaders:haveallinputsandoutputsnecessarytocontroldoorhardware,theyalsohavememoryandprocessingpowernecessarytomakeaccessdecisionsindependently.SameassemiintelligentreaderstheyareconnectedtoacontrolpanelviaanRS485bus.Thecontrolpanelsendsconfigurationupdatesandretrieveseventsfromthereaders.ExamplesofsuchreaderscouldbeInfoProxIPO200byCEMSystemsandAP500byApollo.ThereisalsoanewgenerationofintelligentreadersreferredtoasIPreaders.SystemswithIPreadersusuallydonothavetraditionalcontrolpanelsandreadersmunicatedirectlytoPCthatactsasahost.ExamplesofsuchreadersarePowerNetIPReaderbyIsonasSecuritySystems,ID08bySolushasthebuiltinwebservicetomakeituserfriendly,EdgeER40readerbyHIDGlobal,LogLockandUNiLOCKbyASPiSYSLtd,andBioEntryPlusreaderbySupremaInc.SomereadersmayhaveadditionalfeaturessuchasLCDandfunctionbuttonsfordatacollectionpurposes(.clockin/clockouteventsforattendancereports),camera/speaker/microphoneforinter,andsmartcardread/writesupport.Accesscontrolreadersmayalsobeclassifiedbythetypeofidentificationtechnology.AttributebasedaccesscontrolInattributebasedaccesscontrol(ABAC),accessisgrantednotbasedontherightsofthesubjectassociatedwith160