The IEEE (Institute of Electrical and Electronic Engineers) Task Force worked from 2000 to 2003 before ratifying the 802.3af PoE Standard. The effort paid off as PoE Technology has become a de facto requirement for most User Networks. By powering VoIP Phones, Wireless LAN Access Points, IP Security Cameras and many Emerging devices, the usefulness of PoE is at this point unchallenged.

Key Features of the current 802.3af Standard

• Designed to work on Networks with existing Category 5 and above LAN Structured Cabling Systems utilizing RJ45 connectorization
  
  
• Power Supplying Equipment ( or PSE) can be either Endspan which is an Ethernet Switch with powered Ports or Midspan which is a Power Hub used in conjunction with an existing non-powered Ethernet Switch.
  
  
• Endspan superimposes the power on the existing Data wires (1, 2, 3 and 6). Midspan puts the power on the unused or spare wires (4, 5, 7 and 8).
  
  
• Both Endspan and Midspan techniques are equivalent; neither produces any interference with the Data transmission signals.
  
  
• The amount of power launched by the Endspan or Midspan PSE is 15.4 watts per link (or per Port). Due to loss over the Structured Cabling System, the effective wattage available to the End device is about 13 watts.
  
  
• The End device to be powered is defined as the Powered Device (or PD). The PD cannot care if the PoE signals are coming to it from an Endspan or Midspan PoE source. It is required per the Standard to take power through its RJ45 from either set of pins (1, 2, 3 and 6 OR 4, 5, 7 and 8).
  
  
• The Standard also calls for PoE operation across Standard 802.3 Ethernet Cabling distances (100 meters maximum per link, etc.)
  
  
• Support for 10Mb or 100Mb Ethernet connections for End devices

PoE Plus: The Evolution of the PoE Standard

Work has begun on the next version of the Power over Ethernet Standard. The main purpose of the work is to allow for PoE applications where the End device needs higher power delivery. The working name for this effort is PoE Plus (or poep) and the IEEE has assigned it Official name of 802.3at DTE Power Requirements. Some of the issues facing the task force include:

• How much power to make available to the End device. The amounts the group is considering is approximately 30 watts at this time. No decision has been made on this point.
  
  
• How much power will bundled cables in the Structured Cabling System be able to withstand and still maintain proper integrity. Power equals heat. Too much heat buildup can damage bundled cables. Testing is underway in this area.
  
  
• Support for Data throughput of 1000 Base-T (Gigabit Ethernet)?
  
  
• Should 10G data throughput be considered?
  
  
• Backward compatibility for current 802.3af products

Watch this space for updates and news on the Standards for PoE Plus.