, the SPA921 VoIP Phone is ideal for a residence or business using a hosted IP telephony service, an IP PBX, or a large scale IP Centrex deployment. The SPA921 leverages industry... Connect directly to an Internet Telephone Service Provider or connect to an IP PBX Speakerphone. Caller ID. Call Hold, Transfer, Conferencing, and more Easy installation... or business using a hosted IP telephony service, an IP PBX, or a large scale IP Centrex deployment. The SPA941 leverages industry leading VoIP technology from Linksys to deliver...