I wrote a half page dissertation on my ESI audio problems and erased it.

I'll simply say, ESI will tell you they don't support all models of headsets (even Plantronics)

I doubt it's going to be "an adjustment"

Two questions: "Is the mic "hot" after you've hung up with a caller"

What do the serial numbers on the back of the IP phones start with? (first 4 or 5 digits after any leading zero's)