Power Over Ethernet (POE) has been with us for many years, allowing for signalling and power to be transmitted simultaneously over the same structured cabling, saving cost and installation time. 

Protecting Ethernet lines is a challenge, as we have to deal with power and signalling lines separately. Often there is a misunderstanding in how POE is applied (modes A and/or B) as well as dealing with 4-pair and legacy 2-pair systems. 

This article aims to show how protection measures for POE can often be poorly applied, adding costs yet often resulting in exposing the application to damage.