Crosstalk on analog pots lines. 1

[STMorin]

I moved a branch office to a new building and we intend to install VoIP as soon as a WAN connection is installed. CallManager is in home office. We had the cable contractor pull CAT5e to all the offices and I installed 4-line analog phones for temporary use until T1 is installed. I used the second CAT5 in each office to carry the 4 analog lines and split them into two RJ-11 jacks (each with two lines) that terminate in the phones. At the DMARC, the lines terminate in a 66 block where the 4 lines are distributed. The users are reporting, while on one line, they can hear the conversation occuring on another line. Each line has its own pair in a singe cable to each office; blue, orange, green, brown. Each office has its own home run to the DMARC.
The phones are RCA.

http://www.rca4business.com/products/pc/viewPrd.asp?idcategory=11&idproduct=7

Can anyone give me some insight as to what is causing this? I have run multiple lines over a single CAT3 cable before without a problem.

Thanks
Steve Morin

 

[SYQUEST]

These cheap types of sets have been known to cause line crosstalk. It could be one set or several, that have some sort of internal imbalance that is causing the problem. You might try unplugging one or two of them and see if the condition changes. Double check the jack terminations to make sure no wires are touching. The key issue is loop balance, what is done to TIP has to be done to RING.

....JIM....

 

[allisland]

Did you check the lines at the demarc,with your wiring off?
The line cords going to the stations aren't the flat kind with no twists?
How loud is the x-talk backround or can they actually talk to each other?

 

[STMorin]

The cables going to the phones are flat. I can understand if there was a problem with the phone itself, but a 25 pair cable has minimal twist...just enough to keep the pair together. The lines at the DMARC were clear...I didn't hear any dialtone from adjacent lines. I used the phones for several days before the move. I didn't hear any evidence of crosstalk. They say they can understand every word of what's being said on another line.
No wires are touching. I used modular jacks. Nothing is touching on the 66 block either. I was diligent about cabling and tested each phone as I went.
Problem is, I'm in SC, they are in TX. I'll have them unplug phones one by one to see if the crosstalk stops. There are 9 phones in place.
Thanks

Steve Morin

 

[allisland]

Flat cords are noted to cause x-talk, see if it's just between line 1 and 2 or 3 and 4 and not 1 to 3 or 4 etc,if so it could be the cords

 

[donb01]

I know you have RCA phones, but I use Panasonic multi-line phones and those have CONF buttons that lock down and connect 2 lines together. If someone pushes the wrong button it stays that way until they un-push it.

Don't know if yours have manual conferencing buttons, but it may be worth a look. All it takes is one of them.

 

[whykap]

Can they hear the ring back also or just x-talk?
I'd say you have tip and ring crossed between two of the analog lines causing this.
Double check your x-connects since you do not have this problem on the D-mark when you isolate it.

 

[ISDNman]

I agree with syquest, try a different phone to test with.

I also like whykap's idea - if the phones are cheep this could be an issue. Also, if users want to conference you will need to have tip and ring matched at each line to be conferenced.

By the way, most telco's don't care about Tip Versus Ring anymore, so check at the 66 block first and then work your way out making all are the same polarity once they get to the set.

 

[LkEErie]

Let's go back to how you split the pairs. The first RJ would be pins 54 and 36 to make a paired RJ-14. The second set is 12 78 to keep the pairs intact. You would have to split this out in this manner ON BOTH ENDS.

If you have done this and still have crosstalk, I'd start by only connecting one phone in one leg and disconnect all others, then start adding phones until you find the error.

Do I need to mention that you get what you pay for

LkEErie

 

[jerryreeve]

I really hate 4 line phone sets, Customers love them 'cause they are less expensive (CHEEP) than a phone system but from a tech side they are tough to troubleshoot.

I look at this as there are three possible problems with crosstalk Outside wiring (telco's problem), Inside wiring (your problem), or telephone set. and I go about troubleshooting this with easiest resolution first: find out from customers what lines are experienceing crosstalk and then listen with butt set on one line and put your toner on the other line, If you hear the tone then you can at lest verify that the customer has not lost their mind. next I isolate the line that has the toner from the telco (pull the cross connect to the telco. and see if the problem is inside or outside. If inside then disconnect EVERY telephone by pulling the wall cord at the telephone, listen with Butt set on the one line and put tone on the other line and see if you hear the cross talk. If no cross talk then add one phone at a time until you hear cross talk and isolate bad phones as you go. if there was cross talk then you get to pull all of the cross connects and add them in one at a time until you find out which cross connect/house cable is giving you the problem.

Now since I see you can't do this yourself and the customer probably has no equipment to test with you can't go with my preferred method. First thing is identify what lines are actually cross-talking and if there are only two you can swap a suspected bad line with a known good line at the demark and see if the problem moves by this I mean if lines 1 and 2 are cross-talking then swap lines 2 and 3 at the demark and see if the cross talk moves (from the customers point of view) from line 2 to line 3, if it does the problem is outside. If not you can have the customer unplug all but two phones and see if they are getting the crosstalk on them. If they are then try two other phones to verify that the problem is not the first phones you tried. If it dosen't matter what phones are plugged in and you still have the crosstalk then you probably have a problem within the house cabling (other possiblilty is that all phones are flaky) as far as isolating a crosstalk on house cabale you end up pulling either all legs off at once and putting them on one at a time or pulling one leg off at a time until you isolate since you are looking at doing this in SC while you are in TX I would just suggest calling in a tech, it will save you tons of time and would have saved me a bunch of typing.

----------------------------
JerryReeve
Communications Systems Int'l
com-sys.com

 

[STMorin]

I appreciate everyone's advise with this issue. It appears that one user reported that her line three was everyone elses line one. (2 jacks on the back of the phone, one for lines 1-2, the other for 3-4.) This means that the RJ11 cables going to the phones were swapped. I had the user swap them back and the distracting crosstalk was gone. She said there was a very small amount, but not enough to worry about considering the temporary nature of these phones. VoIP will be installed when the WAN is installed.
Again, thanks for your help.

Steve Morin