Using CAT5E Cables with RJ11

July 9, 2005 at 07:35:56
Specs: WIN2000 Pro, PIII/64 MB

Hello There!!,

I am laying a Simple computer network but the network is supposed to be for both Data and Voice. Is it possible to use the CAT5E cable to be crimped with RJ11 so that Phone connection could be laid down in the same Network plug instead of using the standard Phone cables. If possible i would like to know the color codes for the RJ11 Connector with CAT5E Cale.


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July 9, 2005 at 09:22:39

Yes it is possible to use the cat5 cable for both voice and data. But, I would not recommend it. Cable is cheap enough (about 10 cents a foot or less, CAT3 for the phone is even less). Just pull a parallel cable for the telephone. Also you may be getting some of the new ethernet devices that could use the presently unused strands. If possible never use non standard terminations, it will cause more problems when the next person works on it. There is a good chance the ring signal will couple over to the data causing interference.

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July 11, 2005 at 00:50:35

Thanks for your help. My problem is how to get the CAT5E Cable to work with RJ11 Connector. What is the color codes to be used so that the Telephone connection could be establised.


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July 11, 2005 at 10:37:46

Just use the any of the unused pairs. You could have two phone lines. I still wouldn't do it. Wire is too cheap too risk the problems of interference. I usually have spare runs for networking and phones because it takes more than twice the effort to climb ladders and pull the cables through conduits the second time around.

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Related Solutions

July 13, 2005 at 11:25:37

listen to wizard-fred. run separate cables for voice and data.

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August 1, 2005 at 11:36:15

It is not recommended to combine LAN and telephone wiring into one cable. Some of the reasons have been given earlier in this thread.

Previously some people used a method to do it but have abandoned the practice because of growing sophistication of network standards making with RJ45 configuration utilizing previously unused pin-connections. It is not cost-effective now since the cost of wires and components has come down. It can become incompatible as the newer networking standards come online.

The information and caveats below may help you to make your decision. You may realize that no longer the effort is worth the return.

An issue unmentioned in the threads earlier is about incoming phone lines. In the older methods of providing telephone access, still in place in many communities, the incoming phone lines are potential entry points of huge voltage surges from lightening or other sources that can fry up the adjacent network signals with unpredictable results to your network. Some phone equipment has surge suppression built into it, but your network may be vulnerable. Not a daily event, still it is an important consideration.

Although I do not recommend it, but if you want to tinker at your own risk, use the blue pair on CAT5 wired as 4,5, for red and green of RJ11 and use 1,2,3&6 (orange and green pairs) for ethernet. In RJ45 the blue pair corressponds to the 2 center wires of RJ11 (red,green) automatically.

In RJ45 (T568B standard), pins 4,5 (blue pair)and 7,8 (brown pair) are undesignated. Therefore they could be used for purposes such as phone traffic. In a single line service, RJ11 and RJ45 corresspondance is via the 2 center wires is inherent. For two incoming phone lines there is no RJ11 and RJ45. Non-standard connection of 2nd line via pins 7,8 is theoretically possible but not a good idea.

If you just want to use CAT5 for telephone wiring then consider the following:

CAT5 connectors (RJ45) have 8 contacts (4 wire pairs); standard telephone jacks (RJ11) have 4 contacts (2 wire pairs).

If you have 1 phone line, use the center pair (Blue/Blue-white) in the CAT5 cable, and cut-off/leave all others unconnected. Connect the CAT5 pair to the R & G (red and green)-of the standard phone jack.

With 2 or more lines, use one of the twisted pairs in the CAT5 cable for each line, strip the sheath from the other end, and connect each pair to a separate RJ11 jack for each line. Then distribute the lines accordingly.

RJ11 can accomodate two lines. Some multi-line phones and adapters can separate/use both lines. Some older phone modems/equipment may not operate correctly if 2 live lines are connected to the input. If needed, this can be prevented by using a line cord to the equipment with only 2 wires connected through to each end.

Another helpful piece of information is the standardized color order of RJ11 and RJ45. This can be easily found through an internet search. Basically, the order on RJ11 is BRGY (blue, red, green, yellow) on one end of the cable and reversed on the other end so that B always ends up with B on the opposite end, R with R, etc. The socket side corressponds accordingly. RJ45 is wired straight through or crossed-over. Consistency in keeping the standard should be maintained to avoid technical problems and future confusion.

Hope all this information helps


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