Question Can I use RJ45/RJ45 splitters to run phone and internet on one Cat5e cable?

Aug 2, 2019
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So in our living room there is only one RJ45 socket in the wall which is used for a home phone right now, but we would like to install an access point there to cover that area with WiFi as well.
On the other end there is our router and the Cat5 cables hanging free and running to the other rooms (we don't have a patch panel).

After some search I thought I will use 2 of these RJ45/RJ11 splitters, but they are not available in my country.
Then I thought what if I use 2 RJ45/RJ45 splitters like these, but I found this site and realized the two types of splitters might have different wirings inside them.

Is it okay to use RJ45/RJ45 splitters for this problem if I punch down the end of the cables right? (And if I first figure out the wiring inside the splitter somehow, because none of them come with a diagram in my country.)
Also there is a common line in webshop descriptions for these products in my country which goes "Not capable for sharing internet." I guess that's there for those who think can split the internet signal with only 1 splitter and run it to 2 devices. Anyway, that red text is kinda worrying, so correct me if I'm wrong.

Any advice is welcome. Thanks!
 

R_1

Judicious
Herald
those should work.
I would just wire both ends on the cables.
cat 5 only uses 4 wires of the 8 leaving 4 wire for two phone lines.
wired correctly a single line can do what you want.
these adapter/splitters you are looking at do just that but in a pretty plastic shell.
 
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It maybe simpler to make you own.

In general you can plug phone (ie rj11) into rj45 and they will work. The reason it does is the middle pins overlap even thought have different numbers. BUT this only works if you have all 4 pair of wires. When you use a rj45 splitter only the pairs that connect to pins 1,2,3,6 are used. The center 2 which are pins 4,5 are not and those are the most commonly used for phones.

What this means is most commercial rj45 splitters will not work with phone lines without another adapter of some kind.

What you could do is replace the wall plate on the one end. Buy one that takes a rj11 and rj45 keystone. Then remove the blue and brown pair of wires from the current rj45 keystone and move the blue pair to the rj11 keystone. You can move the brown pair if you want.

On the other end you can cut off the rj45 plug and split the wire with the orange and green pair going to a new rj45 plug at the same color locations and then crimp the blue pair into the center of a the rj45.

The other option is to buy 2 new rj45 keystone and a rj11 keystone. You would plug the existing rj45 into one of the new keystones. On the back you would connect the green and orange pair to the second rj45 keystone. You would then connect the blue pair to the terminals on the rj11 keystone that represents the middle pair.

OR you could just spend the extra money and get a rj45/rj11 splitter on both ends. It is a trade off do you the work or do you pay someone else to do it.
 
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As a second though maybe you do what I did. They had so many fees and charges on the land line and they still charge for long distance I just went VoIP. Magic jack is one of the better known kinds but there are many.
Although there are actually free VoIP services there are many that are better and cost a tiny fraction of the cost of a land line.

Most people just cancelled them completely and went to cell phone only.

Verizon just laid off huge numbers of their employees that do land lines. Maybe if they charged a better rate and did not constantly increase it people would not be moving to other technology.
 
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Aug 2, 2019
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The other option is to buy 2 new rj45 keystone and a rj11 keystone. You would plug the existing rj45 into one of the new keystones. On the back you would connect the green and orange pair to the second rj45 keystone. You would then connect the blue pair to the terminals on the rj11 keystone that represents the middle pair.
This is a good idea I've never thought about. I would be able to make my own splitter that I'm familiar with, and I wouldn't have to mess around much with the cable hanging 2m high from the wall at the router. I just plug them in.
 
Aug 2, 2019
6
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10
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In general you can plug phone (ie rj11) into rj45 and they will work. The reason it does is the middle pins overlap even thought have different numbers. BUT this only works if you have all 4 pair of wires. When you use a rj45 splitter only the pairs that connect to pins 1,2,3,6 are used. The center 2 which are pins 4,5 are not and those are the most commonly used for phones.
So if I cut down the end of the phone cable which has wires at 4, 5 positions, and put on a new RJ45 head with the two wires in position 1, 2, would it work with an RJ45 splitter? I know this is a bit barbaric, but still one of the best choices if it works.
 
This is where looking at picture of wiring pin outs helps a lot.

phone jack have 6 pins. The center 2 are called 3,4. on rj45 the center pins are 4,5.

You can not use pin 1,2 on the rj45 because there is no connection between pin1 and any pin in the rj11. So you can not use the pairs 1,2 and 7,8 This leaves 3,6. These corresond to pins 2,5 on a rj11.

Be careful a rj11 fits a bit loose in a rj45. It works but you do not plug/unplug it a lot.
 
It will all work as long as the wires end up in the correct place. The equipment has no idea what color the wires are or what pins you run them through.

I am unclear how you intend to put the phone wires into pins 1,2 unless you are not using rj11. If you crimp a rj45 onto a phone cable it will work.

Be aware you really want rj45 designed for flat cable and not the more common round cables. You can put phone cable into normal rj45 but you must be very careful because the wire is only being held by the pins if the cable gets pulled it can pull out. Then again people make ethernet cables and do not firmly crimp the jacket into the back of the plug and have the same issue. Also be aware phone cable many times have stranded cable and you need different ethenet plugs for that.
 
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