Electronic Design

PoE Networks


What is the basis for Power over Ethernet (PoE)?

The IEEE 802.3af standard for PoE enables data terminal equipment (DTE) to receive power over the same cabling used for data in an Ethernet network. The standard specifies the protocol for delivery of a nominal 48 V dc over unshielded twisted-pair cables (such as CAT-5). This eliminates the need for a local power source.

What does IEEE802.3af cover?

The IEEE 802.3af standard presents the requirements for providing and receiving power over the existing Ethernet cabling. It involves power-sourcing equipment (PSE) that provides the power on the cable for the powered device (PD). The figure shows a simplified version of a typical PoE system.

What are some typical PDs employed in PoE?

PDs include VoIP phones, security systems, and point-of-sale terminals.

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