National Standard PoE Switch Subdivision

Standard PoE switches are subdivided into PoE (802.3af), PoE+ (802.3at), and PoE++ (802.3bt Type 3 and Type 4), each defined by power output, voltage, and pin usage.Overview of Standard PoE SwitchesA standard PoE switch delivers both data and electrical power over a single Ethernet cable while negotiating the correct voltage with the powered device (PD) to prevent damage. These switches comply with IEEE standards and are also called active PoE switches . Non-standard or passive PoE switches, in contrast, provide constant voltage without negotiation, which can damage devices not designed for PoE .Subdivisions of Standard PoEIEEE 802.3af (PoE)Output Voltage: 44–57V (typically 48V)Max Power per Port: 15.4WUsable Power at Device: 12.95WApplications: Low-power devices like basic IP cameras and VoIP phones IEEE 802.3at (PoE+)Output Voltage: 50–57V (typically 54V)Max Power per Port: 30WUsable Power at Device: 25.5WApplications: Mid-power devices such as advanced IP cameras with PTZ features and wireless access points IEEE 802.3bt (PoE++)Type 3:Max Power per Port: 60WUsable Power at Device: 51WApplications: High-power devices like high-end PTZ cameras and multi-radio access pointsType 4:Max Power per Port: 100WUsable Power at Device: 71.3WApplications: Very high-power devices such as LED lighting systems and advanced IoT applications Power Delivery ModesMode A (Alternative A): Power is delivered over the same pairs used for data (pins 1, 2, 3, 6)Mode B (Alternative B): Power is delivered over spare pairs (pins 4, 5, 7, 8)4-Pair PoE (4PPoE): Power is delivered over all four pairs simultaneously, used in higher-power standards like 802.3bt National Electrical Code (NEC) ConsiderationsThe NEC 2017 edition specifies restrictions on PoE systems to minimize thermal rise in cable bundles. For example:IEEE 802.3af and 802.3at use four conductors, while 802.3bt and Cisco UPOE use all eight conductors TIA-568 compliant horizontal cables require a minimum of 24 AWG conductorsCurrent limits per conductor are defined to ensure safe operation in bundled installations SummaryThe national standard PoE switch subdivision is primarily based on IEEE classifications:PoE (802.3af) for low-power devicesPoE+ (802.3at) for medium-power devicesPoE++ (802.3bt Type 3 and 4) for high-power applications Each subdivision defines the maximum power, voltage, pin usage, and safety compliance, ensuring reliable and standardized deployment across enterprise and campus networks .