Users Guide

Table Of Contents
Switch Feature Overview 75
Power over Ethernet (PoE) Features
Dell EMC Networking PoE switches implement IEEE 802.3af and IEEE
802.3at functionality as well as legacy (capacitor) and pre-standard PDs
detection. IEEE 802.3bt capability is also supported on the N2200 model.
Moreover, additional protections, such as short circuit and dV/dT protection
upon startup, are supported.
PD Detection
The PD detection feature detects a valid AF or AT load, as specified in the
AF/AT standard. PD detection is based on four different voltage levels
generated to the PD (the load), as illustrated in the following figure.
Figure 2-1. PD Detection
Legacy (Reduced Capacitor) Detection
In cases where legacy detection is enabled, the PD Detection mechanism
detects and powers up legacy PDs as well as AF/AT-compliant PDs. This
mechanism is designed to detect and power up pre-standard legacy PDs.
Classification
The classification process takes place immediately after PD detection has
successfully completed. The goal of the classification process is to detect the
PD class, as specified in IEEE802.3AF and AT standards.