Vonage is the largest U.S. provider of residential voice-over-IP (VoIP) service. With E911, emergency dispatchers can see the address where the 911 call originated. Vonage’s E911 adoption is up from 26 percent at the end of November 2005, when a deadline passed for VoIP providers to offer E911 to their customers. AT&T disputed Vonages complaints, calling them “vague” and calling the company’s complaints a “hodgepodge” of issues.”]
Source: https://www.csoonline.com/article/2120402/vonage-e911-availability-nears-85-.html