911 Calls May Not Work (VoIP)

Remember that the 911 network was designed to be supported by and make full use of the circuit-switched network. VoIP uses packet-switched networks. This is a colossal difference that needs to be clearly understood.
At the same time, understand that most 911 calls are local calls to local emergency centers and law enforcement agencies. The major cost benefits associated with VoIP are not realized with local calls. Until the PSTN adopts VoIP and packet-switching, you have to maintain local POTS telephony service for local calls. Such lines can easily be used to make 911 calls directly. You don’t have to lose your ability to make 911 calls just because you’re converting to VoIP for all your toll calling.
On the consumer side, some low-end VoIP providers offer workarounds to enable their customers to let go of their POTS services and be fully VoIP. This is crazy. If you have an emergency, you want the fastest connection possible to 911. Why would you want a service that routes your emergency call out to the Internet, then to your VoIP provider, then back down to a POTS line, and finally to the local 911 center? My recommendation to consumers is to use DSL or cable modem for your Internet services; you can’t get VoIP otherwise. Use the VoIP connection for all your toll calls and videoconferencing services. Plug a POTS telephone into your broadband VoIP adapter box and maintain at least one POTS line for local service.
Lastly, do not be fooled into thinking that you can use your cell phone to call 911 and thereby eliminate the need for that speedier $25 per month POTS line. Even a cell phone has a delay that is longer than what you would get from a standard POTS line. When you are mobile and on the road, you have no choice but to use your cell phone to contact 911. But in your home or business, there is no reason not to have a direct connection to your local 911.