Unlike traditional telephone lines, VoIP numbers can’t be traced by 911 operators. This doesn’t mean you’d be helpless in case of a natural disaster or Sasquatch attack, however. Upon initial setup at a location, you simply need to enter your info manually through the system’s E911 (Enhanced 911) feature, which will attach a physical address to your VoIP number.
While there are still a few other legacy protocols around, and a few non-SIP standards, such as H.232, SIP is what's used for the vast majority of modern VoIP phone systems. The most common use I've seen for H.232 has been in dedicated video conferencing systems. SIP, meanwhile, handles phone service, video conferencing, and several other tasks just fine, which is why its use is so widespread. Where it has trouble is with data security, but more on that in a bit.  
Fortunately, most of the providers reviewed here have engineering staff that will contact you as part of your setup process to help your IT staffers test and optimize your network prior to deploying their solutions. That's definitely something we recommend, but there are steps you can take now to prep your LAN for VoIP and make the deployment process that much easier.
Types of Services offered	Home VoIP, Business VoIP, SIP Trunking, International Calling	Home VoIP, Business VoIP, International Calling	Home VoIP, International Calling Plans	Small Business VoIP, Residential VoIP, Reseller VoIP, Hosted PBX,	Home VoIP, Business VoIP, International Calling Plans	Home Phone Service, International Calling, Business Phone Service

There are some solutions to this issue if you have concerns. The most obvious is to utilize Uninterruptable Power Supplies (UPS) for those short outages, or a generator if you live somewhere where outages are more common (and for your fridge!). With so many people having cell phones these days most people will not be too concerned with this issue, especially when they consider the money they are saving. Most services include a call forwarding feature so you can always set that up to go to your cell phone so you do not miss important calls.
Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet telephony, broadband telephony, and broadband phone service specifically refer to the provisioning of communications services (voice, fax, SMS, voice-messaging) over the public Internet, rather than via the public switched telephone network (PSTN), also known as plain old telephone service (POTS).

The following table provides a high level summary of how residential VoIP service compares to other alternative solutions for home phone service. The table compares this service to a regular landline, a bundled phone service from a cable company such as double or triple play, and a cell phone service. The cell phone is included as some people decide to just get rid of their wired phone and use their cell phone for all calls. Free services such as Skype are not included as they are not effective, like for like, landline replacements in our opinion.
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