Conference Call Line Noise

[dakotatech]

I have a Partner II in a 5 slot carrier. Since we moved buildings, we have a loud screaching noise that appears on occasion when doing a conference call. This problem didn't arise immediately, but has grown worse over the last couple of months. The noise may appear when the 2nd line is attached, or it may start part way thru the conference call. If the loud noise isn't present, then every person hears a metallic echo on the other two party's voice. The problem occurs no matter what lines are used for the conference call, but doesn't occur during any normal call.

I have done the following with no improvement:
grounded the processor
replaced the processor with identical unit
swapped out the cabinet
used a different A/C power source
used the phone lines from the business in the next unit

The only thing that did make a difference was to replace the Partner II processor with a Partner ACS R3.0 processor. The ACS changed the symptoms to just a loud "chirp" that only lasts a second or two when the third party is connected. It still has the annoying echo when the other people talk.

I tested the ACS in and out of the cabinet with no difference. I had a technician try installing resistors in series on both the tip and the ring sides to keep the line balanced. He tried one set, two sets, and even three pairs in the two test lines with no change. I have also had the company doing the system testing install a loop current regulator from Mike Sandman, but it didn't make any difference with the ACS processor installed.

Hopefully someone can figure this puzzle out. I'm at a loss. :-(

 

[telprog]

Yes I have ran into this problem before it's not your system it's the lines at you new building. You need what is called a 90A Attennuator that goes between your lines and the KSU. I've only ran into this problem once but after I put the 90A's in all was good. Get ahold of your Avaya rep

http://www.tel-programmer.com

 

[dakotatech]

I have located the references to the 90A attenuator listed in thread688-727924. I did a bit of research on the

http://independenttech.com

site. As far as I can tell that attenuator is nothing more than a manual version of the loop current regulator that I used from

http://www.sandman.com/loopcur.html.

They also have an attenuator version that you must adjust the dip switches to get the correct setting. The loop current regulator automatically regulates the loop current down to 25ma with no loss of audio level on the line. As I stated in my original post, we tried just resistors, and we tried the loop current regulator because we believe that it is what the problem truely is. The only unknown is that did the regulator actually cause any change? Did it work properly?
I wasn't on site to validate the connection method or the results.

 

[telprog]

As I posted, I've only ran into this problem once and it was on a ACS R3. I went round and round on it until I called my rep who sent me one 90A for each line, It cleared it right up and haven't had any problems sense. I haven't run into that problem ever again so I haven't had a chance to try anything else. Keep us posted as to your results.

http://www.tel-programmer.com