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IP Phone working over Cat 3 Cable

I have a customer that is intending to install Call Manager across their organisation but part of it has only Cat 3 Cabling. It is planned to change this cabling out in the future but will they be able to run a 7900 phone on it in the mean time.

My understanding is that Cat 3 will run fine if statically set to 10Mbp and does support the dot1q encapsulation so I should be able to connect a PC to the port on the back of the phone, and as I've got all four pairs, I should be able to use powered switches or the powered patch panel.

I've got two questions really, will this work ? and is there anything on CCO indicating what TAC will support ?

Many Thanks


Re: IP Phone working over Cat 3 Cable

I am not sure what TAC will say, but I have about 5 users using CAT3. I was forced to do this temporarly, and it has worked fine. The main issue with CAT3 is signal loss. It is not as "twisted" as CAT5, so you have more attentuation. The persons that are using it here are less than 25 feet from the switch (yes they are using POE also). They have not had any problems; it has been like that for a bout a month.


New Member

Re: IP Phone working over Cat 3 Cable

We ran our 79xx's and PCs with inline power for 6-8 weeks on Cat 3 cabling (and hybrid feeder cable, too!) while our Cat 5 re-cabling was completed. Throttled back the speed to 10Mb and everything was fine. These were relatively short distances (< 150 feet). It isn't supported and I wouldn't recommend it for the long-term, but it works.

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