Power over Ethernet (PoE) is an established technology that extends the capabilities of Ethernet signaling by providing low-voltage direct current (DC) power delivery to network devices over the same wires that currently carry data.
Since acceptance of the IEEE 802.3af Power over Ethernet standard in 2003, equipment vendors have been designing standards-based products that leverage the numerous advantages and benefits offered by PoE (see diagram below). Under IEEE 802.3af, 15.4 watts (W) of power are available for each powered device, which is adequate for most current PoE applications.
New standard IEEE 802.3at, commonly referred to as PoE Plus, is expected to be ratified this year and would increase power delivery up to a minimum of 30 W for more power-hungry devices, such as motorized pan-tilt-zoom (PTZ) network cameras, electromagnetic door strikes, proximity sensors or other security devices.
To implement PoE in a new or existing Ethernet network, customers have a choice of varied solutions that include PoE-enabled network switches, midspan power sourcing equipment (PSE), powered patch panels, and single port injectors. The most appropriate solution depends upon each customer’s requirements for:

• Scalability, such as power capacity and port growth — Will the network be impacted minimally by future growth and changes, or will network overhauls be required?
• Flexibility, such as moves, adds, and changes — General-purpose devices such as IP telephones undergo significant movement in an enterprise. However, security devices are installed in permanent locations and are seldom moved. What degree of flexibility does an enterprise require?
• Manageability, such as simple power injection versus endpoint control and power monitoring â€” What level of device control and monitoring will users need?

Benefits and Capabilities of PoE

PoE offers two benefits that are consistent across applications: cost savings and flexibility of device placement. Because PoE runs data and power together over the same cable to each device attached to the local area network (LAN), devices can be installed without concern for the proximity to individual AC outlets. This saves money by eliminating the cost and time associated with AC outlet installations while providing the flexibility to locate PoE devices where performance is optimum.
Additional benefits of PoE include manageability of power sources and battery backups to protect against outages and power spikes. By using a centralized power source, PoE offers the ability to remotely power connected devices on or off in the event of service disruptions or reconfigurations.
PoE also helps protect network investments, because it is an extension of the established 802.3 Ethernet protocol and is supported under 10Mbps, 100Mbps, 1Gbps and eventually 10Gbps data rates. Although no devices take advantage of 10Gbps data rates and PoE, it is only a matter of time for equipment vendors to recognize a need for this high data rate, such as for multimedia communications.
These capabilities and benefits have helped PoE gain rapid interest for communications applications such as voice over Internet Protocol (VoIP) telephones and wireless access points (WAPs).
Security applications such as network surveillance cameras, electromagnetic door locks and radio-frequency identification (RFID) systems are beginning to see wider integration with PoE due to reduced power demand from clients’ devices and greater availability of pre-standard PoE Plus equipment.