One more consideration for protection: Should the protection be deployed on the IC or driver side of the coupling transformer, or should the protection be deployed on the line side of the coupling transformer? Or both? Protection on the driver side of the transformer will benefit from the fact that the magnetics of the transformer itself will limit the amount of energy that will be let through to the protector. Also, the transformer will greatly limit the amount of common-mode energy that will get by the transformer as the interwinding capacitance is usually quite small. Since PoE is applied only to the line side, the PoE issues will not enter into the protection scheme considerations on the driver side of the transformer. There are advantages to placing the protection on the line side, however. Because the protector will limit the amount of energy and voltage to which the transformer will be subjected, the transformer can usually be smaller and cheaper which helps offset the cost and real estate aspects of the protection scheme. Furthermore, for those installations where overcurrent protection is required, protection must be placed on the line side of the coupling transformer.