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IP/Ethernet twisted pair polarity


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#16 mikefamig

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Posted 29 December 2016 - 12:22 PM

I just removed the cable from the socket and there is no voltage to be found on the line coming into the house from outside. I put them back the way that the installer had them and I'm going to call it a day.

 

It is clearly not ring and tip but it does provide high speed IP for my internet and tv.

 

Mike.


Edited by mikefamig, 29 December 2016 - 12:22 PM.


#17 mikefamig

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Posted 29 December 2016 - 12:32 PM

What we have here is FTTP or Fiber-To-The-Pole. I think that it may be IP that is coming into the  house on the twisted pair.

 

Mike.



#18 pete_c

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Posted 29 December 2016 - 01:33 PM

ahh...yes when I got Verizon FIOS they ran the fiber to a box on the side of the house. 

 

I helped when it was installed but have never DIY'd installed a fiber connection to my home. 

 

I just didn't want willy nilly drilling in the side of the house cuz it was new such that I managed and watched the installation.

 

Attached File  fiosbox.jpg   40.47K   4 downloads

 

In the box you could run coax or ethernet cable to the router.  The telephone dmark was plugged in to this box separately a few feet away.  Telephone/fiber box power / backup was connected inside of the house close to the telephone dmark.  

 

During construction I ran coax and ethernet cable from this side of the house to a central closet area in the middle of the house.  I did the same on the other side of the house for a satellite dish. 

 

If your modem is using two wires in an RJ-11 cable then it is not ethernet coming from the pole.

 

In the United States, ADSL is popularly known simply as “DSL,” which is a misnomer, since VDSL is also a type of DSL connection. Differently from ADSL, VDSL also allows the transmission of TV signals, so to the end user, VDSL is more similar to (and competes with) the cable TV system. Another characteristic that puts this system closer to the cable TV system is the use of fiber optics outside the service provider’s building, as we will see. In the U.S., popular VDSL networks include AT&T’s “U-verse.”

 

On DSL technologies, the limiting factor for speed is the length and quality of the cables used by the phone company, since it uses regular phone cables (twisted copper pair). VDSL solves this problem by reducing the length of the standard cable by installing an optical node closer to the user’s home, and the connection between this optical node and the service provider is done through fiber optics, while the connection between the node and the user’s home is done using standard telephone wires. This is exactly the same idea used by the cable TV, except that cable TV uses coaxial cables instead of telephone wires.

 

VDSL goes a step further, and allows the optical node to be installed closer to the user’s point of installation, shortening the regular telephone wires even more, which allows higher speed rates. VDSL even allows fiber optics to be delivered directly to the user’s home.



#19 mikefamig

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Posted 29 December 2016 - 02:40 PM

So given that my system is vdsl/uverse I ask my original question.....does the polarity of the wires matter? I have run them both ways and the dslreports.com speedtest shows that there is little or no difference.

 

Mike.



#20 RAL

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Posted 29 December 2016 - 03:08 PM

So given that my system is vdsl/uverse I ask my original question.....does the polarity of the wires matter? I have run them both ways and the dslreports.com speedtest shows that there is little or no difference.

 

 

I think the answer is similar to my earlier answer for ethernet, as VDSL also uses the twisted pair to transmit a differential signal.  At the lowest hardware level level, yes, polarity matters.  But the equipment that your line connects to is smart enough to correct for reversed polarity.  Your tests showing equal performance when you reverse the polarity proves that.



#21 mikefamig

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Posted 29 December 2016 - 03:15 PM

I think the answer is similar to my earlier answer for ethernet, as VDSL also uses the twisted pair to transmit a differential signal.  At the lowest hardware level level, yes, polarity matters.  But the equipment that your line connects to is smart enough to correct for reversed polarity.  Your tests showing equal performance when you reverse the polarity proves that.

RAL

 

Why did my VOM not show DC or AC voltage on the pair? Is this a very low level square wave pulse or AC signal?



#22 RAL

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Posted 29 December 2016 - 03:45 PM

RAL

 

Why did my VOM not show DC or AC voltage on the pair? Is this a very low level square wave pulse or AC signal?

 

On a differential pair, the goal is to have little or no DC voltage present (called common mode voltage).  Receiving circuits can tolerate some DC common mode voltage, but there are limits.

 

So I wouldn't expect the VOM to show anything if you try to measure DC voltage.  The data bits represent a high frequency AC waveform, but a VOM might not be able to measure it as an AC voltage since they are usually optimized for 50-60 Hz measurements.



#23 mikefamig

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Posted 29 December 2016 - 04:46 PM

Thanks. I did read how in a differential pair the signals cancel each other out pretty much eliminating cross talk. I think that I get it now.

 

Mike.






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