My house was built around 2005, though I've only owned it a year. Setting aside from the insane cluster of coax wiring we found in the attic, I'm trying to understand why every room in the house has at least one, and usually two outlets that look like the attached pictures - two coax connectors, and two RJ11 cables connected to a single splitter. As I'm trying to figure out how best to get wired ethernet to various parts of the house, can anyone help me understand the purpose of this setup? Is it as simple as wanting the ability to put a TV and phone on every wall in the house? It doesn't seem like a pro did the work, especially considering the rats nest of coax in the attic.

faceplate removed

faceplate in place

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    Back before wifi became so reliable a lot of folks wired for internet and satellite throughout, hoping to be future-proof. Wire is relatively cheap, and it's easier to do it at construction time. I suspect that the splitter was a later modification for phone service or something else.
    – isherwood
    May 12, 2020 at 15:46
  • Can you pull enough of the two blue wires out of the wall to see what's written on them and how many pairs are inside? can't see if they're 4pair (ie 8 wires) or 2pair (4 wires) If they're 4 pair then each can be an ethernet link, but if they're only 2 pair or cat3 rated then this bodge was intended to combine them into one ethernet lead.
    – Criggie
    May 13, 2020 at 0:44
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    Just note that those RJ11 jacks are done extremely poorly. Even the short grey one is bad.
    – Nelson
    May 13, 2020 at 8:21
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    @isherwood "wifi became so reliable" [citation needed]
    – JBentley
    May 14, 2020 at 8:08
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    Are you sure that the splitter is just a splitter, or could it be combining phone lines on two jacks into one for a multi-line phone? In other words, are both cat5 cables running back to the phone panel, or does one go somewhere else in the house such as the next room? May 14, 2020 at 15:47

7 Answers 7


Most likely this was a satellite dish hookup.

Back in the 90s, when the technology was nascent, each box got its own LNB feed from the dish. You'd also need an antenna hookup to get local broadcasts (as in two separate cable feeds). The phone line was so the satellite box could phone the company and report whatever purchases were made via the remote (like pay per view)

It doesn't seem like a pro did the work, especially considering the rats nest of coax in the attic.

In the earliest days you didn't have a whole cottage industry of professional installers like today. Instead, you had a lot of installers who doubled as local sales associates and it was merely a side business for them. My parents had one installed in their rural house in the mid 90s by a man from a nearby town who ran a hardware store. As such, you'd have some strange things done by installers (like using a phone duplexer to join lines).

Most modern installers don't even bother with your attic nowadays. They run it around the eaves of your house, then drop it down and straight through the outer and inner walls.


I'm curious if those are all bundled together into one cable in the wall? I have used cable that contained all 4 in one to simplify running it.

Notice that the two coax are different colors so the person wanted to be able to tell the difference between them. To me this implies a separate CATV and Satellite line, but it also could be cable internet or security cameras or many things. The blue cables appear to be cat5, but with only the center pair of each being used. This might have been done if one served landline phone and the other served something like a voip bridge like Magic Jack. They're in the splitter so that one will serve as "Line 1" and the other as "Line 2" to typical multi-line telephones.

If your goal is cable and Ethernet to each room I think you're in great shape! You need to find out where the Ethernet goes and hope they all go to one place instead if being bonded up in the attic.


There might be many answers to this but as someone that had both satellite and cable tv in the past this could be the reason for 2 coax drops in each rooms. For the modular connection that looks like someone used a cat 5? Cable for phone. Using the 2-1 device ties the cables together and not all the conductors are used so that was possibly their way of doing the phones without patch panels or punch down blocks. I have not seen that method used since cat 3 days. There could be other reasons but I have seen and wired dual coax drops but not the phone / data like that unless only phone.


I had a similar system wired in my house. They ran a 6 pair cable to every room in the house and connected them all together in a junction box with a 6 pair to the Bell pedestal.

They also ran two coax to each room. One set was run outdoors for CATV and the other set was hooked up to an indoor antenna located in the attic for local TV. I've actually kept that hooked up because that way, when we lose cable, I still have the locals.

  1. A two into one is for either for data line and phone, which is the most likely reason. While the input is two sets of four wires, only two in each set is active. The single R11 plug will provide phone connect to the phone and the other pair provides data connection to the data line. The data line was a voice line dedicated to a modem for people who needed data connective for a long period of time. Using the modem prevented incoming calls and also prevented you from making a call, so two lines were required.

  2. The same setup is sometimes used to connect two phone lines to one outlet. A two line phones is plug in, and the phone can connect or answer calls coming into either phone.

  3. The third use for this type of connection was for two phone lines, one for voice, and the other was a fax machine. Older phones were POTS (Plain Old Telephone System) with no intelligence, same as the fax machine. None of these after 4 rings, the fax machine would pick up the call.

For installing wired ethernet into every room, you will need Cat-6 or Cat-6 POE or newer types of ethernet cables to support the bandwidth.
The existing wires cannot support this. You may be able to use the wires to provide a map of the path to use to route new wires or to assist in pulling the wires through existing holes through the header and on to the outlets in the wall.


It sure seems that they had DSL at some point. To run DSL you need a line for data and another for phone. Also depending on company (DSL setup) you cannot just "disconnect" (or cut) the phone line as the lines are looped at a point and the phone line is used to help meter (filter) the line to certain specs.

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    A DSL data signal came in over the same phone pair. A DSL/phone filter box was plugged into the outlet and provided two outlets, one for voice and the other for data May 12, 2020 at 17:17
  • this is the real answer, the others are speculative.
    – dandavis
    May 13, 2020 at 16:02
  • DSL does not explain having it to every room whatsoever. You'd only have the unfiltered line to the DSL modem, which would just be in one place. (Technically DSL often allows multiple modems, but it's not a setup that makes sense or that's cost-effective for typical customers who are paying $10/mo to "rent" each $20 DSL modem.) May 13, 2020 at 16:44

Cable TV was originally analog, often delivered over two co-ax cables because one cable didn't have the bandwidth for all the channels offered. Even today you'll often find dual co-ax still strung here and there where no one has bothered to remove it. Until two years ago the cable TV wire attached to my house was dual, with one half just sort of hanging down in the weather.

A house built in 2005 might have been wired up by someone used to putting in dual co-ax, and nobody had gotten around to telling him about the digital age.

  • 6
    Do you have a source for "one cable didn't have the bandwidth for all the channels offered"? I have never heard that before and I can't find any information about it. My house was built in 1979 and has two coax cables in many places, but that is because one of them was for Cable TV and the other was for local over-the-air broadcasts from an antenna in the attic. At least as far back as the 1990's my grandparents had every channel available in the New York metropolitan area and all of them fit on a single cable...
    – Moshe Katz
    May 13, 2020 at 4:02
  • The only thing I could find is that Satellite TV providers would often require multiple coax cables in order to record one program while watching another, but that's just because of how they chose to design their multi-tuner equipment - in fact both cables go to exactly the same receiving dish.
    – Moshe Katz
    May 13, 2020 at 4:03
  • @Moshe Katz: Sorry no citation. I didn't take photos or keep a log then, and I can't find any reference now. - I just remember helping several neighbors move and reconnect set boxes - Most (but not all) free channels were on cable A, and most (but not all) paid channels were on cable B. May 13, 2020 at 12:15
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    I wonder if one of the cables was really just the over-the-air channels from a central antenna in a high location. That's the origin of Cable TV - delivering OTA signals from a mountaintop to customers in a valley who can't access them.
    – Moshe Katz
    May 13, 2020 at 13:27

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