In my case the machine runs perfectly between telephone socket and Zyxel 870H-53a v2 VDSL2 modem. The adapter has seemingly no power dampening effect that lead to connection problems or a lower transmission power. VDSL running at me with the same performance. Possible cause of malfunction in other reviewers I can therefore only assume that the Adpter possibly been connected the wrong way round, a generally poor signal quality at DSL connection or a defective modem / router. Installation instructions are included with the APC product as a special patch cable in which some wires are sheathed in the plug with a small metal sleeve. I can not judge what the good is, but therefore it is recommended to the included cable material from the unsecured side to use.
I can not say anything except that there was no failure at the first storm on the protective power even ;-)
