Installation guide

Matrix DFE-Gold Series PoE Module Hardware Installation Guide C-1
C
About PoE (Power over Ethernet)
ThisappendixprovidesanoverviewofPoweroverEthernetTechnologyandhowitis
implementedinrelationtothe4H4285‐49.
Overview
PoweroverEthernet(PoE)referstotheabilitytoprovideoperationalpowertoadevice
connectedtoadatanetworkusingthesamecablingthatprovidesthedatainterface.
ModernEthernetimplementationsemploydifferentialsignalsovertwistedpaircables.
Thisrequiresataminimumoftwotwistedpairsforasingle
physicallink.Bothendsof
thecableareisolatedwithtransformersblockinganyDCorcommonmodevoltageonthe
signalpair.PoEexploitsthisfactbyusingtwotwistedpairsasthetwoconductorsto
supplyadirectcurrent.Onepaircarriesthepowersupplycurrentandtheother
pair
providesapathforthereturncurrent.Whileseveralproprietarylegacyimplementations
ofPoEhave beendeployedbyLANequipmentvendors,in2003theIEEEpublishedthe
IEEE802.3af‐2003specification,whichispartofthe802.3suiteofstandards.
The4H4285‐49isfullycompliantwiththeIEEE802.3af
standard.Itsupportsthestandard
resistorbaseddetectionmethod,aswellasACdisconnectcapability.The4H4285‐49is
alsocapableofsupplyingthemaximumspecifiedcurrenttoallportssimultaneously.
EachPDhasaPDC(PoweredDeviceClassification)thatistransmittedtotheDFE module
forpowermanagementpurposes.Table C‐1
onpage C‐1liststheclassificationsandthe
associatedpowerranges.
Table C-1 Powered Device Classifications
Class Usage PD Maximum Power Range Usage
0 Default 0.44 to 12.95 Watts
1 Optional 0.44 to 3.84 Watts
2 Optional 3.84 to 6.49 Watts
3 Optional 6.49 to 12.95 Watts
4 Not Allowed Reserved for Future Use