Just got my TriStar H81N Plantronics headset. The instructions said just plug in the cord and it should work. Once plugged in I cannot hear a dial tone in the earpiece. There is nothing else in the instruction manual about how to get a new headset working. The phone its plugged into is a Avaya 9608.

Audio Players & Recorders - Plantronics - TriStar H81N Noise Canceling Earset Over the ear