Conference calling problem - possible cabling issue

[vitaliyz]

Hi,
one of my offices experiences a strange problem with conference calling. The 2nd party and the 3rd party don't hear each other very well. The person who initiated the call hears both of them perfectly though, and so do they.

There are two phone systems in the office: Merlin Legend and IPC and the problem exists on both. Also this is not phone company provided 3-way calling, but actual conference calling.

This leads me to a conclusion that wiring is somehow screwed up somewhere, but I'm really out of ideas here. The whole thing just doesnt make sense.

I would really appreciate any suggestions or tips!
Thanks in advance

 

[LkEErie]

If you didn't take Physics or sound engineering, here's the deal. When you call from A to B, the circuit has a certain loss that is inserted so the call "sounds" good. When you call from B to C the same loss is present. A-B and B-C sounds good.

Now, look at the call from A to C. The loss that was inserted into "B"'s midpoint has just been added to the A-C connection.
Whoops. Double the loss, and now they can't hear.

There are solutions to this, most notably, Central Office based conferencing, VoIP conferencing, VoIP trunking, etc.
Certain phone systems can be set to compensate for this loss, your two aren't those.

LkEErie

 

[vitaliyz]

Thanks for the answer. I definetely thought of that.
The thing is that one of our other offices has the same PBX and same analog trunking, but doesn't experience the problem.

 

[LkEErie]

I didn't have tha problem either when my office was about 100 cable feet from the Central Office

The phone company is not obligated to give you any particular exchange grade line loss. It can be from ZERO to about -11.5dB. They strive for -3 to -6, but it's not a given.
A VoIP line, like from Vonage using Motorola ATA's is adjustable. IF you plan on a lot of conference calls, look into a solution like that.

LkEErie, who doesn't endorse Vonage or any other VoIP company

 

[ignatkarobkin2]

Vitaly What kind of phones are you using for Conferencing?

http://www.aaa-avad.com

http://www.ivdsonline.com

 

[ignatkarobkin2]

Forgot to answer your question.
Good things about cabling is it either works or doesnt. Since you are able to dial out and dont hear static the problem is in your system.

http://www.aaa-avad.com

http://www.ivdsonline.com

 

[DallasBPF]

it wouldn't 'hurt' to double check your punch downs for that cable in the conference room and the IDF it connects to, BUT that being said I would still look to the provider. Have you tried to replicate the same sceario in a different room in the same building on the same phone system? Do you get the same outcome or does it work fine?

If same outcome, definetly look at your CO or possibly your PBX might need a software upgrade? Does your other office and the current office having the problems have the same version of software?

------------------------------------
Dallas, Texas
Telecommunications Tech
CCVP, CCNA, Net+

CCNP in the works

 

[vitaliyz]

Thanks for the answers! Defintely going to try those suggestions.

There are two completely different systems - Merlin Legend and IPC Turrets, both having the problem.

Also some of the lines are POTS and some are FLEXGro. I'm going to see if the problem appears on both - it might help to see if it's the line issue.

 

[ignatkarobkin2]

When you say both having a problem. Do you have one conference phone connected to both systems?

http://www.aaa-avad.com

http://www.ivdsonline.com

 

[vitaliyz]

No, the problem happens with all different phones, so the phone is out of the question.

 

[DallasBPF]

Ok, lets break this down a little bit;

1) does it only happen on that one cable when you plug in multiple phone types?

2) does it happen to any phone on any cable in the building?

If 1 then you need to check your cabling... if 2 you need to contact your provider.

Also, are these phone lines on a PRI or are they individual POTS lines, does it happen continually on every conference call or is it random? If random and POTS, isolate the correct POTS line and contact your Telco company. If constant and POTS, probably your PBX. If constant and PRI, could be PBX and/or Telco...

------------------------------------
Dallas, Texas
Telecommunications Tech
CCVP, CCNA, Net+

CCNP in the works

 

[trvlr1]

This may be an environment issue, especially if they are conducting the calls handsfree. When you test, try muting the phone when you are not speaking and see if you still have the issue. It could be that the phones you are using (1 or more) may be a simplex phone, only carrying conversation in one direction at a time. When on handsfree especially, background noise from one of the other sites could interfere with your transmission. This is especially prevelent in rooms with hard walls and lots of windows. And just because you have a high quality phone, does not mean that the same goes for the other callers.

Just a thought in a different direction than cabling issues!

 

[AWGoodson]

Its not a wiring problem!

Check to see if the phone system that started the conference call provides amplified conference. If does not then evertime you add someone to the conference the volume will decrease even more.

Allan Goodson
Estimator
3D Datacom, Inc.

http://www.3ddatacom.com