I had a conference bridge card installed on a Electra Elite IPK. The bridge card (16) is setup for (2) bridge callers with a total of 8 callers in each bridge. Callers are able to enter the bridge fine, its the 5th to the 8th caller we start getting a feedback sound and all persons in the bridge call can hear a high pitch sound after they speak. Also, There was a Memory upgrade as well done to the IPK for a total of 192 ports. What setting on the IPK needs to be changed to stop the feedback?