建筑自動化設備使用網絡的力量

　　建筑自動化設備使用網絡的力量

　　以太網供電（POE）提供了一convenient DELIVER路兩個電源和數據連接兩個遠程設備使用一個單一的電纜。這使得它的功率傳遞的解決方案，是高度的兩suited建筑自動化系統(tǒng)和一個協議，承諾的問題與許多現有的網絡，往往是基于一個混合的專有協議和連接。

　　許多建筑物已經具備大規(guī)模數據基礎設施的基礎上通過10BaseT和100BaseT以太網所需的5類電纜。這減少了新的布線需要連接各種樓宇自動化設備，如IP視頻攝像機和RFID閱讀器以及無線接入點，可以提供擴展連接到無線，電池供電的傳感器節(jié)點數量。

　　PoE takes advantage of the fact that a Cat5 cable contains four pairs of wires. Although later， higher-speed Ethernet standards transmit data on all four pairs， only two pairs are used for sending bits under the 10Base-T and 100Base-T standards.

　　The most recent version of the IEEE 802.3af PoE standard makes it possible to provide up to 25 W of power to a remote device， with some vendors going beyond some of the restrictions in the standard to extend this to just over 50 W or to improve overall efficiency. The lower aggregate resistance of doubling the number of pairs reduces transmission losses. The IEEE has formed a task force to develop a standard for four-pair PoE that would allow for increased power delivery and improved efficiency. The task force expects the standard to be ready in 2017.