Using CAT5e cable as standard phone line

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I would like to move my DSL modem to another room. My choices for connecting it are:

1. Go under the house, run a phone line to the new room, and install a phone jack there for the DSL connection.

2. Use an already-existing CAT5e patch cable which already goes under the house from the old room to the new room for the DSL connection. Accomplish this by using a CAT3 to CAT5 adapter on each end of the CAT5e cable, in effect converting the existing CAT5e cable to a standard phone line.

I would prefer to use option two, since I already have a cable run going where I need to go. But I’m having a hard time finding CAT3 to CAT5 adapters. I’ve found a couple on Amazon, but they have negative and positive reviews, which leads me to believe that there is more to this than simply plugging a CAT5 to CAT3 adapter on each end of the CAT5e cable.

Does anyone have any experience with this type of thing; and does anyone know where I can get a pair of CAT5 (female) to CAT3 (male) adapters? The existing CAT5e cable is 568-B, if that makes any difference.

Thank you.

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Been doing that for the past 5 years, without the adapters. My place has jacks in the wall for either Ethernet or standard phone line. Some rooms only have one jack, and it takes both cat 5 connectors and regular RJ-11 phone connectors. The wire behind the jack is cat 5, so it works for me, strangely enough!

Our house was pre-wired for Ethernet, but they also used cat 5 for some of the jacks that were meant to be either Ethernet or regular phone. Those jacks accommodate both RJ-45 and RJ-11 (modular phone) connectors. Dunno how else to explain it!

However, in order to ensure that it works, you MUST use the middle two contacts in the jack for the phone line, either black and yellow pair or red and green pair. By pair I mean one wire colored yellow and one wire colored black is one pair and one wire colored red and  another colored green is one pair. Those are the standard color codes for phone wiring inside the house in the U.S. at least.

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The nomenclature for these cables can be confusing.  Ok, not “can be…”  They are confusing.

The CATx numbers reference the cable specification in reference to data speeds and maximum lengths for a given cable, not the connector type. CAT5 cable is still CAT5 even if it is still on the spool in bulk and has no connectors on it yet.

The connector usually used with CAT5/5E/6 cable is 8 position, 8 contact, or 8P8C, more commonly called RJ45.  The RJ specifications are really for the combination of the jack/plug and the way it is wired, but in the way people use the terms, it’s usually just about the plug size.  RJ45 isn’t an official designation, but it is used informally to refer to the 8P8C connector when wired in the standard way for ethernet communications (T568A or B).

RJ45s is an official designation, but it is only 8P2C, with only one wiring pair used.  Physically, the connector is the same size as the unofficial RJ45, but is keyed (it has an extra little tab that sticks out that prevents it from going into a RJ45 jack).

A standard phone jack or plug has 6 positions with only the center two being used (single pair).  The connector is thus 6P2C (six position, two contact).  The assembled phone cord using that setup is called RJ11.

Another common phone jack or plug has four contacts (this is what my VDSL modem uses; two pairs, which means that as far as the wiring is concerned, it uses two phone lines).  The plug and jack are 6P4C, with the assembled cord called RJ14.  Most of the time, assembled cords of this type are mislabeled as RJ11, since people think RJ11 refers to the size of the jack or plug.  It’s really only RJ11 if it uses only one pair of wires.

The least commonly seen phone plug is 6P6C, with three wiring pairs, and referred to as RJ25.

What kinds of problems are people describing with the adapters?  I’d say just grab any one you see that is in the right format and try it.

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Ascaris wrote:

What kinds of problems are people describing with the adapters? I’d say just grab any one you see that is in the right format and try it.

Some of them say that the adapters don’t work. Also, it seems like some people say that you have to use the middle pair of wires, while others say you can use any pair.

I don’t want to cut my Ethernet patch cable, because it is a store-bought patch cable. I was hoping to simply get an adapter which would allow me to plug the Ethernet cable into the DSL wall jack on one end, and another adapter which would allow me to plug the Ethernet cable into the modem DSL jack on the other end.

Like you say, I guess I can just go to the store and buy whatever adapter they sell (if they sell this sort of thing locally), then try it out.

Thanks for the info.

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1. Perhaps the ease of your project may depend on your DSL modem model & service provider.
2. You can buy the stuff to make your own.
3. Here’s an ebay seller link, use of this would be at you own risk. (Does that exactly match what you were wanting to use? RJ-45 female to RJ-11 male)
4. There is another destructive, possibly costly now & future way to get a phone line by splitting the cable allocating two or four wires for the phone line from that cat 5e cable. You will need to get the RJ-11 jacks, crimping tool (if you do not have already have a RJ45/RJ11 multi-tool) and perhaps some preferred branded sealant to prevent moisture ingress at the cable ends.

I hope this has helped you in someway.

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You can use any pair, as long as its a pair, not wires from non-pairs.
I assume your phone connector is too small to plug the CAT5 cable in and you need an adapter. As long as you buy two adapters the same then they will use the same wires and the connection will be OK – assuming they are wired correctly.

cheers, Paul

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Not really much to add to the debate as such but as Network cable generally has a degredation of signal at around the 50m\60-65ft mark and particularly  doesent like to be forced in to tight acute angles, kinks etc such are the perils of running cable and coupled with the cost. It could well be advisable to go with the phone cable solution and cheaper too.  If that doesent work out in the interim with the connection to\from, block\box  adapter to P.O.T.S (surprisingly, Plain Old Telephone System) as phone cable has significantly less degredation due to the voltage, conductor involved and nature of the signal, going back to my electronics days. If memory serves me right the Internet comes across the Phone system using the TDM concept (Time Division Multiplex) hence you can receive Phone calls and Voice traffic on the same line with out loss of quality. Used to be if you had a friend in the Phone company you could get them to tweak the gain on your phone line for better dial up, but the voice quality “Su***d. I am Sure you already know about any connection(s) has to be well made\tight and kept to a minimum to avoid loss through resistance and the like. Anyways that’s about the only thing I can suggest hope it helps.

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Jim, I done this a few years back whilst our house was undergoing DIY improvements.

From our main router I connected a 25m Cat5e extension cable from number 1 lan Gb port of the four and fed it under the floorboards to another router/repeater in a different room. The beauty of this method is, if I need to upgrade either router, it’s just unplug the Cat5e extension and replace. This made possibilities of network expansion very easy in future without the need for wireless.

I didnt opt for wall mounted sockets so I could pull through the Cat5e cable should we decide to move house or if something went wrong with the Cat5e, I could tie string between the old and replacement and pull it through with a minimum of fuss and headaches. On entry and exit of floorboards I have larger rubber grommets in situ in order to do this.

Never looked back as this improved network connectivity speed over wireless, which I never really trusted/embraced anyway. Yes I’m old hat but, it works great for us.

Edit: Have you considered POE plugs (Power Over Ethernet) which utilise the existing electrical circuit copper wire as a form of connectivity? Downside of this is having an electrical socket near your location in respective rooms.

If you like this idea, remember to use the AskWoody ‘buy from Amazon’ button to the right of the forum interface

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If he likes to listen to shortwave radio broadcasts, power line over Ethernet adapters are known to have been a source of radio wave spectrum pollution.

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The same can be said about wifi frequencies and certain home appliances.

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True, moving a short distance way from the emitting appliance may resolve the problem most of the time. If possible changing the wireless channel to the least crowded that moment on the 2.4Ghz or 5Ghz frequencies does wonders for a terrible connection.

If the devices you suggested he use do bleed all over the spectrum similar to what this fellow recorded and this example, then it is a problem. Surely if a device is going to turn your power lines in to large broadcast antenna they could perhaps keep it quiet.

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I’m thinking of just getting a pair of adapter plugs and trying it out. If I can find them at a store in my community, and they don’t work, I can get my money back.

I can’t imagine it not working, no matter which two wires I choose in the Ethernet cable, except for one possible consideration: If I pick two wires which aren’t paired in the Ethernet cable, they won’t be the same length due to the different number of twists for the different pairs. Not sure if that matters for DSL phone wire.

Worst comes to worst, I can leave the router where it is and use the existing cable to put a switch in the new location, giving me a few Ethernet ports there. Really, I’ll need only one in the new location, because only one of my computers doesn’t have wifi; so as a last resort I can use the one cable to achieve the Ethernet connection for that one computer.

In reality, I’m looking for any way I can to avoid going under the house. It was a bit traumatic the last time I went under there, because I tend to be claustrophobic.

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