Designed for the "essential" user profile, the 9640 has the identical button layout and form factor as the 9630. The key difference is the 9640 supports a brilliant 1/4 VGA color display. The 9640 is ideal for telephone intensive executives, as well as for those workers who benefit from phone applications.  Available via free firmware download, the 9640 and 9640G support SIP telephony features along with additional SIP enhancements - including display of  telephone "presence" of other users from the phone contact list, integration with MS Outlook calendar appointments, changeable display skins.  SIP on the 9640 / 40G includes enhanced security features such as support for SRTP and TLS.

Avaya 9640 Datasheet