Here's what I've found...
The 6930 phones - They have 4 RJ connections on the back. They've moved connections around on the back of the phone from one REV to another.
Of the phones I've seen, from RIGHT to left...
the port farthest to the right, is identified with the headset icon is to be used with the handset - It can be used with a wired headset (Plantronics Polaris was tested), but you have to lift the handset to make it work.. and of course, this disabled the use of the handset itself.
The phone then has an Ethernet port that goes to the network and pulls PoE. Followed by another Ethernet port that will go to the workstation.
Then another 8-pin connector with an adapter to allow for a handset type 4P4C connector to fit without it flopping around. This is identified with the HANDSET icon. However, this port does not appear to work at all - with handset or headset.
Above this adapted connector, is a USB port.
According to the documentation, you must use a USB headset if you want something that's professional grade.
Alternately, you can use a Bluetooth headset or a DECT adapter and headset.
Mitel really did a bad design on the functionality of this phone. And they've done a worse job in documenting it.