资 源 简 介
建筑自动化设备使用网络的力量
以太网供电（POE）提供了一convenient DELIVER路两个电源和数据连接两个远程设备使用一个单一的电缆。这使得它的功率传递的解决方案，是高度的两suited建筑自动化系统和一个协议，承诺的问题与许多现有的网络，往往是基于一个混合的专有协议和连接。
许多建筑物已经具备大规模数据基础设施的基础上通过10BaseT和100BaseT以太网所需的5类电缆。这减少了新的布线需要连接各种楼宇自动化设备，如IP视频摄像机和RFID阅读器以及无线接入点，可以提供扩展连接到无线，电池供电的传感器节点数量。
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.
