PoE and PoE+, why PoE+ is higher power?

http://en.wikipedia.org/wiki/Power_over_Ethernet

"The original IEEE 802.3af-2003 PoE standard provides up to 15.4 W of DC power (minimum 44 V DC and 350 mA) to each device. Only 12.95 W is assured to be available at the powered device as some power is dissipated in the cable.

The updated IEEE 802.3at-2009 PoE standard also known as PoE+ or PoE plus, provides up to 25.5 W of power. The 2009 standard prohibits a powered device from using all four pairs for power. Some vendors have announced products that claim to be compatible with the 802.3 at standard and offer up to 51 W of power over a single cable by utilizing all four pairs in the Category 5 cable.

Numerous non-standard schemes had been used prior to PoE standardization to provide power over Ethernet cabling. Some are still in active use."

PoE provides both data and power connections in one cable, so equipment doesn't require a separate cable for each need. For equipment that does not already have a power or data connection, PoE can be attractive when the power demand is modest. For example, PoE is useful for IP telephones, wireless LAN access points, cameras with pan tilt and zoom (PTZ), and remote Ethernet switches. PoE can provide long cable runs e.g., 100 meters (330 feet) and deliver 12 W of galvanically isolated power. PoE-plus provides even more power.

There are competing technologies. The Universal Serial Bus (USB) provides both data and power, but it is designed for short cables with a maximum length of 5 meters (16 feet) and provides less than 2.5 W of non-isolated power. It is less expensive than PoE, and works well for low power peripherals such as a computer mouse, a headset/microphone, or a serial port. Some peripherals, such as speakers, scanners, and printers, need more power than USB can provide. Firewire (IEEE 1394) is similar to USB, but can provide substantially more power (45 W) but has an even shorter limit on cables at 4.5 m. On the other hand, USB peripherals can operate using very little power; while maintaining an Ethernet connection uses a significant amount of power.

If a device already has power available but no data link, then PoE may not be attractive. A wireless data connection such as IEEE 802.11 may be more economical than running a data cable for the device. Alternatively, there are power line communication technologies that can use power cables for transmitting data. Using some power line modems may be more economical than running a cable.

When data rate and power requirements are both low, other approaches may be viable. Cellular phones, for example, use batteries for power and wireless for data link. Remote weather sensors uses very low data rates, so batteries (possibly supplemented with solar power) and custom wireless data links are used. Replacing batteries is a nuisance, but if the batteries last six months to a year, the practice may be tolerable.

Depending on the application, some of the advantages with PoE over other technologies may be:
Inexpensive cabling
Modest power
Fast data rate
Peer-to-peer network access. Once a device is connected to the network, it is accessible to many users."

Thanks for trying to help, but I'm sorry my question isn't that simple that you can copy the first answer you got from a google search!! cause i did way more than that and i didn't find the answer.. if you are not specialist in electronics or networking please don't waste my time and yours .. but really thanks anyway

Welcome to the Able2Know community. As a community on the whole, most of us are laymen. Some, like myself, are former engineers/techies and also good researchers. In general, there are very few if any in the community who may have exactly the expertise you seek.

You had asked a question in your first post about power handling that indicated you hadn't researched it. So I answered that question and others with posting directly from Wikipedia. Sorry that you thought that was wasting your time. You asked questions that indicated you hadn't done any research.

Hello to one and all,

Axis High Power over Ethernet midspans and splitters offer an easy, fast and cost-effective solution for powering network video products - specifically PTZ (pan/tilt/zoom) and PTZ dome network cameras - without the need to install power outlets and electrical cabling.

Axis High Power over Ethernet (High PoE) midspans and splitters enable Axis network video products to receive data and power over the same Ethernet cable.

The High PoE products make it easier to install network video products in areas where power cabling and outlets are unavailable. Installation costs are thus reduced.

The midspans and splitters conform to the IEEE 802.3at for powering devices with high power requirements on a network. The midspans are also IEEE 802.3af compliant, which means that they can be used with all Axis network video products with built-in PoE support.

The function of a midspan is to inject power into a network cable. A splitter, which separates data and power coming over an Ethernet cable, is used for a network video product without built-in support for PoE.


Thanks and Regards,
Steven Brooks