PoE power supply voltage for the switch

PoE switches typically supply 48 volts DC, with a standard range of 44–57V depending on the IEEE PoE standard.Standard Voltage OutputMost PoE switches output 48V DC, which is the standard for IEEE 802.3af (PoE) and 802.3at (PoE+) devices . The voltage range for these standards is generally 44–57V, allowing for stable power delivery over Ethernet cables up to 100 meters. Industrial PoE switches often adopt 48V to ensure long-distance transmission, strong anti-interference capability, and wide device compatibility .How PoE Voltage is DeliveredActive PoE switches perform a handshaking process with connected devices (Powered Devices, PDs) to detect compatibility and negotiate the required power level . Initially, the switch applies a low voltage to detect the PD, then ramps up to the full 48V DC once the device is confirmed. This ensures safe operation and prevents damage to non-PoE devices . Passive PoE systems, in contrast, may supply a fixed voltage (sometimes 12V or 24V) without negotiation, which can be less safe and may not comply with IEEE standards .Variations and ConsiderationsPoE+ (802.3at): Also typically outputs 48V DC but can deliver higher power (up to 25.5W per port) compared to standard PoE (15.4W per port), .PoE++ (802.3bt Type 3/4): Can deliver up to 51W or 71.3W using all four pairs, still within the 44–57V range .Industrial switches: Some can accept 24V DC input and boost it to 48V for PoE output, useful where standard 48V sources are unavailable .Voltage drop: Over long Ethernet runs, voltage may slightly decrease due to cable resistance, especially with lower-quality cables .Safety and Device Compatibility48V DC is considered a safe low-voltage standard for humans while providing sufficient power for most PoE devices . Devices designed for IEEE 802.3af/at standards are compatible with this voltage, and the negotiation process ensures that each device receives the correct power without risk of overvoltage . In summary, when selecting a PoE switch, expect a nominal 48V DC output, with active negotiation for device power requirements, and ensure your cabling and devices are compatible with the chosen PoE standard.