A Description from telephonyware.com

With improved audio quality over the original Polycom SoundStation IP 3000 conference phone, the SoundStation IP 4000 SIP voice conferencing unit is the answer for organizations that are ready for the benefits and versatility of a SIP enabled business.

Designed for offices or small to medium sized conference rooms, the SoundStation IP 4000 SIP provides remarkable room coverage. You can speak naturally from up to 10-feet away from a microphone and still be heard clearly on the far end of the call. Need coverage for a larger room? The optional extension microphones offer an increased pickup for larger rooms. Plus, with gated microphone technology, echo and background noise is almost entirely eliminated.

Full-duplex conference phone

• Natural two-way conversations
• Both directions of the audio path are active so you can talk and hear at the same time
• Uses Polycom's industry leading Acoustic Clarity Technology
• Self-adjusting operation - the phone automatically adjusts to the room conditions
• Gated microphones reduce echo and background noise

SIP Support

• Conference phone for your SIP enabled PBX (including Asterisk)
• Uses Polycom's rock solid SIP stack

Expandable

• Speak naturally from up to 10 feet away from a microphone
• Optional extension microphones for greater room coverage

Display

• Backlit, graphical 248 x 68 resolution LCD for easy menu navigation
• Informative interface that facilitates easy voice conferencing

Other Features:

• Easily field upgradable
• Up to 2 calls simultaneously (one active, one on hold)
• Context-sensitive hotkeys and scroll keys
• User selectable ring tones
• Easy menu access to Missed Calls, Received Calls, Placed Calls as well as Corporate Directories
• Instant Messaging (IM) and Presence support
• Multi-lingual user interface, with languages including:
  • Chinese
  • Danish
  • Dutch
  • English
  • French
  • Italian
  • Japanese
  • Korean
  • Norwegian
  • Portuguese
  • Russian
  • Spanish
  • Swedish
• Auto provisioning via FTP and TFTP
• Web-based configuration