In order to see the full potential of this type, Cat8 or higher cables are required. Type 4, being the most recent iteration, has not been implemented widely yet as this type allows support for 2.5GBASE-T, 5GBASE-T and 10GBASE-T. The Type 4 (IEEE 802.3bt-2018) iteration is the most recent iteration implemented at the time of writing and uses 4PPoE exclusively because the maximum wattage that can be delivered theoretically is 100W of DC power to the end device. The Alt.A and Alt.B methods are still supported in this standard. The Type 3 (IEEE 802.3bt-2016) iteration introduced the 4PPoE method and supports a theoretical maximum output of 60W of DC power and an increase in heat being dispersed by the cable (up to 10⁰C or 50⁰F). This standard is backward compatible with Type 1 devices, though, Cat3 cabling cannot be used due to the higher power output, and Cat5 or greater cable are the only cables that can be used on this and future standards, as this added support for 1000BASE-T networks Alt.A and Alt.B are compatible with this standard as well. The next iteration, Type 2 (IEEE 802.3at-2009), allows a theoretical maximum of 30W of DC power that can be sent to the end device the length restriction mentioned prior still applies, however, the increased power causes more heat to be given off (up to 5⁰C or 41⁰F) and should be a factor in longer runs. It also should be noted that this standard can be used with Cat3 (maximum of 10BASE-T networks) and Cat5 cables (maximum of 100BASE-T networks) methods Alt.A and Alt.B are compatible with this standard. However, some power is lost in the cable when it approaches its maximum length of 100m. The initial standard, Type 1 (IEEE 802.3af-2003), initially allowed devices to output a theoretical maximum of 15.4W of DC power. A visualization of these three methods is shown below with labels for T568 A and B punchouts. 4PPoE provides electrical power using all four pairs of wires this method allows for higher power usage by the end device. Alt.B transmits the electrical power on the pairs of wires that are unused in the transmission of data on the ethernet cable. The technique used by PoE transmits two complementary electrical signals at once and is interpreted as different signals by the receiving circuit. Alt.A transports power on the same wires as the data, using a technique similar to phantom power, which is used in traditional landline phone systems. The wattage is delivered to the receiving device using one of three methods: Alternative.A (Alt.A), Alternative.B (Alt.B), or 4PairPoE (4PPoE). For the purposes of this post, the focus will discuss PoE as it relates to Access Points (AP). This standard was first standardized in 2003 with IEEE802.3af and has been updated 2 more times since with the most recent, IEEE802.3bt, being ratified in September 2018. Power over Ethernet (PoE) is a term used to describe a set of standards that allows DC electrical power and data to be transmitted simultaneously along the same cable.
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