Here's one for you guys out there. I have a Mitel SX2000 Light and am using a Superset 4150. When I plug my Plantronics headset into the headset port on the back of the phone it works fine for a while then the handset starts picking up noise from the headset wen the headset button is off and then mysteriously the handset voice piece stops working. This is the second phone that has done this to me and I know of one other compliant as well. I simply just can't figure this one out.

Have you enabled headset in cos? Also check the switches on the plantronics unit.

Headset is enabled in cos, headset works fine. Tehre are no switches onthe headset, it's just the headset that plugs directly into the back of the phone

maybe...just maybe...make sure theres not constant feedback thru the headset and keyset, if the user lays the headset on top of the keyset when not in use....just listen for a constant squeal...this may be taking out the the ciucuit itself