Power Over Ethernet Interoperability Guide

Fault Conditions

A basic underlying concept in safety testing is that of single-fault conditions. Safety standards require that the user of any equipment or device be protected, not only under normal operating conditions, but also under overloads and single component failures. In general, abnormal conditions include overloads and single-faults. A singlefault for example, could be just one discrete component anywhere on the PCB, failing either open (perhaps missing altogether in assembly or production) or shorted (perhaps because of its failure mode). For example, the P-N junction of a zener device can simply melt under excessive energy dissipation and finaly fuse in a shorted condition on cooling. Or we could have an inadvertent/intermittent ...