Using coax TV cable for telephone servie

[KimoKeala]

This is what I need. I found a picture, but not a technical description so I can purchase it. I want to use my TV coax cable for telephone service. I want a coax to RJ-11 adapter. If I knew how to post the picture, I could show you folks what I am looking for.

 

[USAFRet]

This is what I need. I found a picture, but not a technical description so I can purchase it. I want to use my TV coax cable for telephone service. I want a coax to RJ-11 adapter. If I knew how to post the picture, I could show you folks what I am looking for.

Detailed instructions on posting images on Tom's hardware.
http://www.tomshardware.com/faq/id-2580030/detailed-instructions-posting-images-tom-hardware.html


However....you can't just get a coax to RJ-11 'adapter' and have a free phone line and a phone number.
There are other, extremely inexpensive ways to do this, but I do not think what you seem to be seeking will work.

So...what are you actually wanting?

 

[KimoKeala]

All I want is to use my spare coax cable as a telephone line. As I understand it, a telephone line needs only a pair (two conductors). So is there some adapter that will use the inner coax conductor and the outside sheath as a pair of pseudo wires so I can use it for telephone service?

 

[USAFRet]

All I want is to use my spare coax cable as a telephone line. As I understand it, a telephone line needs only a pair (two conductors). So is there some adapter that will use the inner coax conductor and the outside sheath as a pair of pseudo wires so I can use it for telephone service?

Telephone service, to where?
As in...a valid phone number that I can call and talk to you?
That won't happen.

Moving a 'phone signal' around in your house? Maybe.

 

[Solandri]

All I want is to use my spare coax cable as a telephone line. As I understand it, a telephone line needs only a pair (two conductors). So is there some adapter that will use the inner coax conductor and the outside sheath as a pair of pseudo wires so I can use it for telephone service?

Phone (and ethernet) cables use a twisted pair. The signal is inverted, and the signal is transmitted on one wire, its inverse along the other. At the other end, you invert the inverse and add it to the original signal. This cancels out (almost) any noise picked up by the pair during transit.

It will not work with coax, mainly because the outer sheath will shield the inner coax from any noise. When you recombine the two, the noise will remain and degrade the audio.

What you're trying to do *might* work with a pair of RJ45 to BNC baluns. Balun stands for balanced/unbalanced. In audio, the inversion trick I described above is called balanced audio. To run a balanced signal (like XLR) over an unbalanced cable (like coax) and vice versa requires a balun - a device which converts between balanced and unbalanced.

Unfortunately most baluns are designed for running video (coax source) over ethernet cable. In theory it should work the other way around. However, I'm not sure which wire pair the baluns use. A phone jack (which will fit into an ethernet socket) uses the two middle pairs. Either you'll have to get a cheap balun, hack off the end of a phone line and rewire it to the correct wire pair of an RJ45 jack. (You don't need to use power - it's for powering a camera via the video cable when there's no power outlet nearby.)

https://www.amazon.com/VIMVIP-HD-CVI-Passive-Connector-Transmitter/dp/B06XCGZ3H5

Or you'll have to get a pair of baluns which lets you access each twisted pair so you can connect the coax to the correct twisted pair.

https://www.amazon.com/uxcell-Channel-Passive-Video-Transceiver/dp/B001WANGQM/

Also, be aware that while the shielding on the coax should help block noise, you can still pick up noise from anywhere else in the house that has a coax outlet. And if you're planning to make phone calls, you'll still need phone service from somewhere. This setup will only work for extending an existing phone connection inside your house to a room without a phone connection.

 

[KimoKeala]

All I want is to use my spare coax cable as a telephone line. As I understand it, a telephone line needs only a pair (two conductors). So is there some adapter that will use the inner coax conductor and the outside sheath as a pair of pseudo wires so I can use it for telephone service?

Phone (and ethernet) cables use a twisted pair. The signal is inverted, and the signal is transmitted on one wire, its inverse along the other. At the other end, you invert the inverse and add it to the original signal. This cancels out (almost) any noise picked up by the pair during transit.

It will not work with coax, mainly because the outer sheath will shield the inner coax from any noise. When you recombine the two, the noise will remain and degrade the audio.

What you're trying to do *might* work with a pair of RJ45 to BNC baluns. Balun stands for balanced/unbalanced. In audio, the inversion trick I described above is called balanced audio. To run a balanced signal (like XLR) over an unbalanced cable (like coax) and vice versa requires a balun - a device which converts between balanced and unbalanced.

Unfortunately most baluns are designed for running video (coax source) over ethernet cable. In theory it should work the other way around. However, I'm not sure which wire pair the baluns use. A phone jack (which will fit into an ethernet socket) uses the two middle pairs. Either you'll have to get a cheap balun, hack off the end of a phone line and rewire it to the correct wire pair of an RJ45 jack. (You don't need to use power - it's for powering a camera via the video cable when there's no power outlet nearby.)

https://www.amazon.com/VIMVIP-HD-CVI-Passive-Connector-Transmitter/dp/B06XCGZ3H5

Or you'll have to get a pair of baluns which lets you access each twisted pair so you can connect the coax to the correct twisted pair.

https://www.amazon.com/uxcell-Channel-Passive-Video-Transceiver/dp/B001WANGQM/

Also, be aware that while the shielding on the coax should help block noise, you can still pick up noise from anywhere else in the house that has a coax outlet. And if you're planning to make phone calls, you'll still need phone service from somewhere. This setup will only work for extending an existing phone connection inside your house to a room without a phone connection.

Thanks for trying to be helpful. But I just went ahead and implemented a rather crude but workable solution and it worked. Like I said, I had a coax TV run from my cross-connect panel to the room where I need the phone (but no phone line). So I took an extra coax cable with couplers on them and cut it in half. Used the center solid copper core and the braided copper outer sheathing and soldered those to some wire lengths that I punch down onto the telephone block with an active line on it, which is also contained in my cross-connect panel. Then just coupled the end of the coax jumper to the vacant coax run using just a barrel connector. In the office/room, I just happened to have an old internal TV antenna in my junk box in the garage, and that antenna had a press-fit coax connector on it. Cut off a short length and soldered the two wires to the two applicable wires on an old RJ-11 telephone cord. Plugged the RJ-11 into the phone jack and the press-fit connector onto the coax nub coming out of the wall. It works like a charm! Just wish I could find the "right" connectors and cables so the solution will look more "elegant". Right now it works great and looks OK, but I don't like the looks of the black electrician's tape I used to cover up the soldered splice joints.

 

[KimoKeala]

BTW Salondri, I still cannot figure out how to post images here. If you have email, I can email you the connector I am trying to find. I was able to find the image on the internet, but there was no technical description associated with it.