Doing an installation involving a Lucent CPU phone system located in basement of large home. New A/V closet is located on 2nd floor where I have 2x2 future wires run to 8 locations where phones will be located. I am not doing the phone system but unfortunetly assumed that a cat 5 home run to each each of these stations would satisfy the telephone man. I assumed that the phone person was going to install a new cpu in the A/V closet and I had 2 future wires going to the basement which could bring up the main lines to the new cpu as well as 1 spare. Murphy's Law changed things and the owner is keeping the old cpu in the basement so I have to quickly run a 25 pair cable thru walls that have already been sheet rocked since the phone person indicated that each phone needs 2 pairs. He did not specify if the 25 pair cable should be cat 3 or cat 5 and is out on vacation and I need to run this cable this weekend. 25 pair cat 5 seems to be hard to get before weekend. people have 25 pair cat 3 and say it is fine for phone and that cat 5 is overkill for phone - cannot afford to make a mistake on this last minute change and do to wiring run I want to run 1 25 pair not multiple cables. Can anyone with phone experience let me know if cat 3 is safe to run which is available or is cat 5 necessary? Any advice will be greatly appreciated.

Cat 3 will work perfectly. There is absolutely no need for Cat 5 for an analogue electronic phone system. Actually, Cat 3 is overkill.

Agreed

Larry
www.fineelectricco.com

yeah.

We always run CAT5 just because that gives us the option of using it for higher-speed connections in the future. Shoe is right; I think CAT1, which may not even exist, is all that is needed for phone signals.

Just to point out: the CAT rating has to do with the number of twists per foot. (If you look carefully next time you strip a few inches of a CAT-5 cable, you'll notice that the different pairs have slighly different twists-per-foot from each other, to reduce the cross-talk between them, too)

Until recent years, telephone cable used simple parallel conductors. In older installations, phone wiring was not pre-wired in-wall, so there was little noise pickup from nearby power wiring.

Since the wiring became the property of the building owner after the monopoly break-up, the need for noise immunity has increased with more phone wiring installations being done inside walls.

Larry
www.fineelectricco.com