Issue link: https://www.e-digitaleditions.com/i/1066130
January/February 2019 I 17 Power over Ethernet (Type 1) IEEE 802.3af-2003 15.4 W 13.0 W 2-pairs 350 mA is to understand how this will change the ICT cabling landscape and installation practices. The "nice to know" is that there are published standards and codes available to help guide the planning and installation for these higher power PoE deployments. Also, it is always a "nice to know" that manufacturers of cabling systems and devices can provide training and design options. But even though there are infrastructure standards for the cabling, there are no specific standards or protocols for the individual devices (e.g., LED lights). It is still a "wild, wild West" as implementation topologies vary among system and device manufacturers. THE POWERS THAT BE To deliver PoE, there must be a power source and a PoE-enabled device to receive the power. The power sourcing equipment (PSE) can deliver a variety of power levels, depending on the requirements of the powered device (PD). All the powering takes place in the network's Ethernet link layer, which differs from plugging a device into an AC outlet. It is important to understand these different types in the selection of powered devices, which must be compatible with the PSE. When a PD is connected to the PSE, power is generated only when a compatible PD detection is found. The PSE discovers how much power the PD is required to draw. The PSE then monitors the power draw and can disconnect the circuit if the PD exceeds a set limit or if the PD is disconnected. There are four "Types" of power delivery over Ethernet as defined by IEEE standards and specifications (see Table 1). Type 1, which was ratified in 2003, addressed a low range of 4 to 15.4 W at the PSE and up to 13 W at the PD (depending on the distance and voltage drop) and is often informally referred to as "802.3af." Type 1 was created to address digital security cameras that were utilizing balanced twisted-pair cabling to connect to an IP network and delivered power over two of the unused pairs. Type 2, which was ratified in 2009, addressed the power needs of more complex security cameras (e.g., pan, tilt and zoom) and delivered up to 30 W DC at the PSE and up to 25.5 W at the PD. Type 2 is often referred to as "PoE Plus." The newly ratified Type 3 and Type 4 use all four pairs of a balanced twisted-pair cable to push PoE to 60 W and above. Therefore, they are often referred to as "4-pair PoE." Because the standards TABLE 1: Overview of power types by IEEE standards. Standard Minimum Power at PSE Output Maximum Power at PD Input Number of Pairs Maximum Current per Pair Power over Ethernet Plus (Type 2) 4-pair PoE (Type 3) 4-pair PoE (Type 4) IEEE 802.3at-2009 IEEE P802.3bt-2018 IEEE P802.3bt-2018 30.0 W 60.0 W 90.0 W 25.5 W 51.0 W 71.3 W 2-pairs 4-pairs 4-pairs 600 mA 600 mA 960 mA