The CyberData SIP-enabled VoIP Ceiling Speaker is a Power-over-Ethernet (PoE 802.3af) and Voice-over-IP (VoIP) public address loudspeaker that easily connects into existing local area networks with a single cable connection. The speaker is compatible with most SIP-based IP/PBX servers that comply with the SIP RFC 3261. The speaker is powered via a standard Ethernet Cat 5 cable - no external power supply is needed. Note: The ceiling speaker calculations are based on equal-sided, unobstructed rooms. For elongated rooms like hallways or for obstructed rooms, additional ceiling speakers may be required.