This may seem a bit "elementary" but our building currently has cat3 cable ran to all of the phone jacks. It's worked well for our old comdial analog system and now our Merlin Legend. I got a good deal on an Avaya IP Office IP406 and I know this is an IP phone system, but will it work with the current cat3 cabling that we have? I've done some research and have found conflicting answers. Running Cat5 or higher isn't an option because I don't know how much longer we're going to be in this facility, and I don't want the headache of running new cable. If Cat5 or higher is required, we'll stick with the Merlin Legend system until we move. All of the runs are relatively short. It's a pretty small building and I'd say the longest run is maybe 60 or 70 feet. They all terminate in the closet to a patch panel and then straight thru patch cords with RJ45 connectors go between the patch panel and the Merlin Legend unit.