The DK 424 (or 280)... Some users, all on a new office area with new phone runs from a demark that existed on their floor, get a very noticable echo on everything. Everything means incoming, outgoing and voice mail.

Having not seen this before, what can cause it? If crossed wires, I would think they could also hear OTHER phones, which they do not. What can cause this and what should I look for? They do NOT seem to be on the same PDKU card, but may be. Reporting of the probem has not been very specific in all reports.

try making a call from the dmark with a butt set

Also try calling over intercom to eliminate the phone/card/processor. If intercom works ok, check the co card.