split pair cabling

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 Question by Pete posted 18 Jun 2004
 split pair cabling
I have built a new house. My electrican wired Cat5 cabling for the phone jacks. I want to know if it's possible to run two phone lines and one LAN line (Ethernet 100MB) off the one Cat 5 cable. How does he do this?
 Answer by Joseph Golan posted 23 Jun 2004
Dear Pete,

It is possible but you may end up with something less then 100BaseT ethernet due to interferenc/crosstalk/EMI and if in the future you need to go to 1000BaseT it will be impossible.

That said, the cable would have to split at both ends with 2 pairs dedicated to the 100BaseT connection and terminating the or/wh pair to pins 1&2 of an 8 pin modular jack and the wh/gr pair to pins 3&6 (follow the color code for T568B) at each end.
For the voice this leaves the wh/bl pair and the wh/bn pair. If you want both lines on a single jack for voice (RJ-14) then line 1 which should be the wh/bl pair will be on pins 4&3 of a 6-pin modular jack and line 2 which would be the wh/bn pair will be on pins 2&5. If you want the 2 voice lines to be on separate jacks (RJ-11) then both pairs would terminate on pins 4&3 for their respective jacks.

Joseph Golan, RCDD

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