We recently installed a TDA200 with 70+ phones all 7600 series phones. The customer started complaining of a squelching tone coming out of the speaker phone on only 8 of the sets. The phones are on 4 different cards sdo I believe that we can rule out a bad card. We have swapped all 8 phones with no resolution. Has anybody heard of this issue before? Panasonic tech support seems to believe that it is an environmental issue. We have tried all that we know to try, our next step is going to be changing out the processor and changing cards one by one. Please help if you can.
Thanks