sundance-communications.com/forum Forums Other TDM Phone Systems Other Telephones & Systems rca 4 line bleeding

does anyone know a solution for bleeding on 4 line sets. this customer has rca sets. i cant find a reason. over the years some people have this trouble and some dont with the same phones. is there anything that can be done. thanks dave

Are you using long, flat, line cords? We found bleed between lines 1&2, and 3&4 on AT&T 954's when using anything other then the provided twisted pair line cords.

One other possibility is that the cabling is wired for T568A or B. I believe the sets are wired as (2) RJ-14, this could cause split pairs and enable crosstalk if not properly "paired".

Is the total length of the cable runs between the stations and the demarc really long?

From working with AT&T 944s, I've found that the longer the runs, the greater the chance of experiencing crosstalk/bleed through.

Over time, the CONFERENCE buttons start getting a little sticky on these types of phones. I'd try moving a couple of phones around, see if the problem travels.

i believe its a mild crosstalk not the kind from a conf button or crossed lines. i think they may be using flat cords but i need to check on that. the cords are starndard length, the demark run is a 25 pr to the ceiling going over several suites to a 25 pr block. from there the station runs arent too long. thanks for the imput. i also need to find out which lines bleed. have a good friday!

If you plug them all into a bunch of modular blocks all wired right next to each other, do you still hear the crosstalk? That would prove that it's not the wiring at fault. It may be just a case of shoddy circuit design within the phones. Does it happen more when the humidity is high?

Whether they are wired 568 A or B would not have any effect, since neither of those protocols splits any pairs.

Did you install it? If not, I would do a very careful examination of the station wiring.
Many sparkies and do-it-themselves types use OR/GR for the first pair, BL/BR for the second pair, and the tips for the 3rd and 4th pairs.

Did they use quad, flat cordage, speaker wire, coax, twin lead, or thermostat wire? I've seen all of the above.

Standard-length mounting cords with parallel leads should present no problem.

If all seems OK, then I would run a separate 4-pair Cat-3 (minimum) for lines 1 through 4 to each station. Cat-5 would be even better, since it has much better cross-talk rejection than Cat-3. *

The best way to test for cross-talk is to dial up 1000 Hz test on one line, place it on Hold, then pick up another line, break dial tone, and listen for the tone. Since cross-talk caused by wiring problems is cumulative, start disconnecting portions of the wiring scheme until you hear a noticeable difference.

* Over to you, Hal.

How many phones are there?

If you have more than 4 or 5 phones, potential for cross-talk increases dramatically.

It is a problem in the phones themselves. I have seen an installation(by others) that was wired with Cat 5 that had incurable cross-talk. They had 8 phones.

they have about 6 phones and i did some of the cable and some was already done. existing is cat 2 or 3. mine is cat 5. now i hear there was a fire in the suite next door in the past. the maintence guy told me some cable had been altered in that suite. he was talking about running new feed from telco. thanks for the imput. dave

then why not CAT6 wouldn't that be much more better ?

wrong type of crosstalk , it ought to be CAT3, CAT4 , 5 or 6 will give you no benefit for voice applications