Authentication - Yes
Voice and Signaling encryption - Yes
802.1X - 802.1X is wireless authentication protocol, not applicable here
Specific plug which permits the connection of different accessories. - the phones have PC switchport as well as RS232 port, and headset ports
separate amplified headset - typically not recommanded and not needed, but may be used if supported
Blue Tooth support - not yet.
HTH, please rate all helpful posts!
Chris