I just installed (4) Avaya 1616 IP telephones and plugged in our older Plantronics headsets (not sure of the model headset however it is a basic set "over the head" with 2 earpieces and a clear plastic micro). When I use the headset I have no problems hearing a caller however the caller cannot hear anyone. This issue is the same with all telephones. I tried turning off AGC on headset, etc.. but no luck. Anyone aware of a one-way audio issue with headsets on a 1616? Perhpas the headsets are not compatible in someway - even though they seem very basic?