Element,Description,Reference
"""FAX""","Indicates that the following GSTN         
telephone number is a facsimile device,
and the message refers to the Internet
Fax Service",[RFC3192]
"""VPIM""","To specify that the GSTN address refers   
to a voice mailbox that is intended to
accept a VPIM message",[RFC3804]
"""VOICE""","To specify that the GSTN address refers   
to a voice device that is intended to be
sent a voice message via an 'outdialing'",[RFC3804]
"""AMIS""","To specify that the GSTN address refers   
to a voice mailbox that is intended to be
sent an AMIS (Audio Messaging Interchange
Specification) voice mail message",[RFC3804]