ofdevices(PLCs,PCs,puters,operatorinterfaceterminals,etc.)work.Access:ALAN'workatatime.essmethods.Collisiondetectioniswherethenodes"listen"work.Iftwonodestransmitsimultaneously,thecollisionisdetectedandbothnodesretransmituntiltheirmessagesgetthroughproperly.Tokenpassingallowseachnodetotransmitonlyifit'sinpossessionofaspecialelectronicmessagecalledatoken.Thetokenispassedfromnodetonode,allowingeachanopportunitytotransmitwithoutinterference.Tokensusuallyhaveatimelimittopreventasinglenodefromtyingupthetokenforalongperiodoftime.hewaymessagesarearrangedandcodedfortransmissionontheLAN.montypes.Proprietaryprotocolsareuniquemessagearrangementsandcodingdevelopedbyaspecificvendorforusewiththatvendor'sproductonly.OpenprotocolsarebasedonindustrystandardssuchasTCP/IPorISO/OSImodelsandareopenlypublished.
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