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?
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 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.

Sincerely,
Joseph Golan, RCDD

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