That wasn’t my question exactly. Let’s omit the phone being used. What is required for any IP phone to accept multiple simultaneous calls? Is it more than enabling call waiting?
The Polycom’s actually accommodate multiple calls without adding additional line buttons - they calls just pop up when offered.
Having said that and having used the 321’s for years (they used to be our standard phone) you would drive the user CRAZY trying to control that many calls with a phone with that small a display.
So yes the phone CAN do it, but you would NOT want to do it - if you are liking the Polycom’s you should look more towards the 650 if you like the SoundPoints or the VVX-410 if you want the next gen phone.