About Power over Ethernet
– PoE or Power over Ethernet gives a description of the standardized system developed for passing electrical power side by side with data over the Ethernet cables.
– The major advantage of this technology is that both the data and electricity can be provided to the networking devices such as closed – circuit TV cameras, network hubs or routers etc.
– This technology is not similar to the universal serial bus which powers the devices over the data cables.
– The difference is that long cable lengths are allowed in power over Ethernet technology.
– The pairs of wires that are found to be extra and ate not used in transmitting data are used the other way i.e., for supplying power.
– Maximum 25 watts are available for every device and it also depends up on which version of the standard is being used.
– There are numerous non-standard schemes that were used earlier i.e., before the standardization of the PoE technology.
– Category 5 cable is required for PoE as per the IEEE standard but it can also operate on category 3 cable when the power requirement is quite less.
– Common mode is used for supplying the power over the different parts of the wire that is used in Ethernet cables.
– A power supply unit within networking device in which PoE is enabled supplies the required power.
– This networking device might be an Ethernet switch.
– There is an alternative to this method for supplying power.
– In this method, the power is injected in to the cable run via a mid-span power supply.
– The original PoE standard of IEEE 802.3af – 2003 was capable of providing up to 15.4 w of dc power to all the devices.
– Since some power gets dissipated in the cable, therefore 12.95 w of power is only available.
– Around 25.5 W of power is provided by the updated PoE standard of IEEE 802. 3at- 2009.
– However, this standard prohibits the use of all 4 pairs by the device for power.
– The data signals of Ethernet continue to travel along the wires namely 1, 2, 3 and 6.
– Power is either routed to the leftover wires namely 4, 5, 7 and 8 or superimposed on these wires.
– The former technique is known as the mid-span technique and the latter one is called the end-span technique.
– The power is picked off by the end device at its RJ45 connector.
– It is then routed to the power circuit of the device.
– The need for powering the end device from a local 110v AC outlet is eliminated completely because of the power over Ethernet technology.
– Some other names for PoE are power over LAN and power injection.
– Using mid-span technique you can save up to 90 percent of what you would spend on traditional powering methods.
Advantages of Power of Ethernet – POE
Power of Ethernet technology is needed because of the following advantages it offers:
- Cuts down the cost of cabling
- Faster data rate
- Does not requires any battery back up
- Provides peer – to – peer network access. Once a connection is established between the device and the network, a lot many users can access it.
Uses of Power over Ethernet – PoE Technology
PoE technology has uses in number of fields such as: