The Federal Communications Commission (FCC) requires that all two-way phone numbers (those numbers that can place, as well as receive, calls) to provide a physical address to emergency 911 dispatchers when 911 is dialed. This is called Enhanced 911.
According to the The FCC's web site, the purpose of Enhanced 911 is to "increase the effectiveness and reliability of wireless 911 service by providing 911 dispatchers with additional information on wireless 911 calls."
This requirement extends to VoIP service providers. Some VoIP services are not yet E911-compliant. Be sure to ask your service provider whether your service complies with the FCC regulations.
