The ACD agents on my IDS 228 system are hearing their own voice echoed back at them with a half-second delay on some but not all incoming customer calls. They are using Digital Display Phones spread out on different LSI port cards. They have new Plantronics headsets. It's possible that all of the problem calls are on one T-1, but I'm not sure yet. Any suggestions as to what I should look at would be appreciated.