I have a customer that we just installed a BCM50 bout a year ago now. They are complaining if echo on line for last 7 months or so. They have 8 pots lines from telco, and maybe 20 or so extensions. Have the main unit and one expansion module on system. We have checked all pots lines and tests good. We removed BCM and installed an old 8x24 for temp and echo was still there. So went back to BCM. We have now moved all lines to Godigital Carrier system on outside of building so its a digital signal from CO to building. Customer says still have echo issue. All wiring in building is new Cat 6 wire which terminates to patch panels with Panduit Mini-com Cat 6 jacks on both ends of cables. Digitals sets get cross connected from jacks with ethernet cables to a panduit voice patch panel back over to the cross connect to the BCM unit. Could it be the wiring, the patch panel or maybe the phones??? We have changed everything I can think of, but echo always comes back.