4-line telephone via RJ45 jack?

I have 4 analog land line service from comast. The 4 lines come out of two RJ11 jacks on the cable modem.
I have a multi line phones (att 1040) that accepts 4 lines via two RJ11 jacks.
This should be simple, just connect two RJ11 jacks from the modem to the two RJ11 jacks on the phone.
Except the modem and the phone is far apart with an in-wall RJ45 (ethernet) cable between them.
Is there an adapter that would take the 4 lines from two RJ11 jacks and convert them to RJ45 jack (that happens to have 8 conductors, or 4 pairs of lines)? If not, what is an accepted way to make this adapter myself?
I can cut one end off an ethernet cable, and also cut off the ends of two RJ11 cables and then solder the wires together. But I'm hoping for a more elegant solution; otherwise I would have to make two such Y cables one at the modem end, and another at the phone end.
There's a Frys electronics store nearby; is that the best store to find phone wiring accessories? I live near seattle.
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Umm... Are you connecting the phones directly to the box from Comcast?
There is a configuration where 8P8C are used for providing 4 telephone lines but it is not called RJ45 (which is actually the jack itself, not how it is wired) it is called RJ61X... If you have it presently configured for ethernet you would need to change the way the the jack is connected to the wires as ethernet wiring standards splits the pairs in ways which makes the configuration not usable for analog telephone connections...
The type of cable you seek might be available, but seems pointless when you can just remove the present face plates or cable terminations which have an RJ45 outlet or jack and install dual RJ11 plates at each location where you need to connect this special wiring for the 4 line phone sets and wire the top jack for lines 1 and 2 and the bottom jack for lines 3 and 4...
Where you would only need to have the conductors available to install to the proper terminals on the back of the RJ11 jacks on the cover plate...
IDC (Insulation-displacement connector) is the preferred method of connecting or terminating telephone conductors, connections on premises and outside plant wiring have not been soldered in several decades...
If you do not have wall mounted plates installed and you are referring to a loose cable you have fished through the wall, there are surface mounted connector boxes which you could use for this purpose...
Good luck...
~~ Evan
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Why not just replace the face plates with a plate that has two RJ11s in it?
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bob wrote:

At the risk of stating the obvious... If you accidentally plug in an ethernet connection and the phone rings, you might not be happy with the result. Sure, you're never gonna do that...right!!!
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bob wrote:

This will cost less than $5
Take a regular phone cord (RJ-11) and cut the ends off with a nice 8" pigtail. Now you have two modular plugs with access to the wire. Strip wires (Red+Green L1) (Yellow+Black L2) attach them to the ethernet cable in this order: (solder and heatshrink would be nice)
Jack 1 (Modem side) (Red+Green L1)= Blue/Blue white (Yellow+Black L2)= Orange/Orange white
Jack 2 (Modem side) (Red+Green L3) = Green/Green white (Black+Yellow L4) = Brown/Brown white
On the phone side, get a double jack
http://www.spywaredrguide.com/VirtualDr/images/dual_RJ11_phone_jack_01.jpg
and wire as such:
Top jack: L1    white-blue    blue-white L2    white-orange    orange-white
Bottom jack:
L3    white-green    green-white L4    white-brown    brown-white
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G. Morgan wrote:

BTW, there are other ways if you don't want to strip wire. let me know.
When you do make the connections, use a "Western Union Splice"; not the type you would make with a wire nut.
The wires are very thin on the jack wire, so you may want to get a 12' cord and cut in half to practice. Once you perfected the stripping of that cable and know how you're you are going to solder and cover, then cut cable to desired 8" (or longer if you want the splice hidden on the floor).
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Physically there are adapters that will go into a single RJ45 and make it into a dual one. There are also adapters that will go into an RJ45 and make it into an RJ11. So, it seems you could plug two of the latter into one of the former and you'd have your dual RJ11. However, not sure about the wire mapping that results. Whenever I think about that stuff a lot of head scratching is required and it's too early in the AM.
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On 12/15/11 4:58 PM, bob wrote:

Is this what you want ??
http://www.telephoneparts.com/index.cgi?pcode 2108
BTW, 2 lines in one 6-pin plug/jack (6P4C) is technically called RJ-14.
RJ-11 is one line in a 6P2C
I doubt you'll find such at a retail store like Fry's, BestBuy, etc
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Yes! Thank you.
I also found a similar adapter, but it cost twice as much and has a possible wiring typo: http://www.hubbellcatalog.com/hubbellpremise/datasheet.asp?PN=BR851241U&FAM=Jacks
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On 12/15/2011 3:58 PM, bob wrote:

I have to custom make adapters all the time in my work when I'm installing phone systems and data networks. If you want to use 4 pair network cable to make your own phone line, use Cat5 cable instead of Cat6 because 6 is a lot harder to work with. You can make your own adapters for either end of the cable using a long enough patch cord cut in half. strip it back and crimp on the smaller RJ11 plugs to matching pairs on either end of the patch cord you just cut in half. When you plug in in on either end of your network cable run the circuits will match up. Besides, the crimp tool for the smaller plugs is a lot less expensive. ^_^
TDD
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Thanks to all who helped. I've learned something new. The most important is RJ45 is not the same as 8P8C even though they look identical. RJ45 is for networking and 8P8C is for phone. There are 4 twisted pairs
RJ45: (4, 5) (3, 6) (1, 2) (7, 8) 8P8C: (4, 5) (3, 6) (2, 7) (1, 8)
For noise free phone operation, it is probably better to find out whether the jacks are RJ45 or 8P8C so the 4 phone lines travel in 4 twisted pairs in the network cable.
Someone has suggested this item which splits a RJ45 connection into two 2-line phone jacks: http://www.telephoneparts.com/index.cgi?pcode 2108
This looks exactly like what I need, assuming the jack in the wall is wired as RJ45 (mostly probably).
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