In September 2005 the IEEE approved the creation of the IEEE802.3at DTE Power Enhancements Task Force.
The IEEE802.3at standard should extend the IEEE 802.3af power delivery and port-level resiliency capabilities and extend the number of applications that could benefit from Power over Ethernet.
The new version of the standard raises the maximum available powered device controller input to 30W in comparison to the 13W of the IEEE 802.3af standard. Some powered devices currently offer 30W of power but use the hand-shake mechanism that the current standard specifies. The Draft 2.0 version of the IEEE 802.3at standard states that an older device that cannot conform to the new classification scheme and relies on the hand-shake sequence should receive only 13W of power and not 30W.
The new IEEE 802.3at standard is still under development but the IEE standards body has finalised the PHY (physical-layer) classification, which allows powered devices and power-sourcing equipment to recognise each other as 802.3at compliant.
802.3at Objectives:
The objectives of the 802.3at Task Force are as follows:
• 802.3at should operate on CAT5 and higher infrastructure, unlike 802.3af, which had take into account the CAT3 limitations
• 802.3at should follow the power safety rules and limitations pertinent to 802.3af
• An 802.3at PSE must be backwardly compatible with 802.3af and be able to power both 802.3af and 802.3at PD's
• 802.3at should provide the maximum allowed power to PD's within practical limits, but at least 30W
• 802.3at PD’s, when connected to a legacy 802.3af PSE, will provide the user an indication that a 802.3at PSE is required
• Research the operation of mid-spans for 1000BASE-T
• Research the operation of mid-spans and end-spans for 10GBASE-T
