The Federal Communications Commission had set the Monday deadline as an interim safeguard while providers of Internet calling, also known as "VoIP" for Voice over Internet Protocol, rush to comply with an FCC order requiring full emergency 911 capabilities by late November.
Vonage Holdings Corp., the biggest VoIP carrier with more than 800,000 subscribers, told The Associated Press Wednesday that 96 percent of its customer base have responded to the company's notices about 911 risks. But that still means as many as 31,000 accounts would need to be shut off as early as Tuesday.
Other leading carriers declined to quantify the response rate beyond the updates they were required to file with the FCC two weeks ago. AT&T Corp. spokesman Gary Morgenstern said customer acknowledgments are now "significantly higher" than the 77 percent figure it reported to the FCC on Aug. 10.
The FCC issued its order in May after a series of highly publicized incidents in which VoIP users were unable to connect with a live emergency dispatch operator when calling 911.
Vonage, AT&T and other carriers have indicated that they plan to comply with the FCC deadline to disconnect customers.
"There is no way to know just how close (to a 100 percent customer response) we will get by Monday," Vonage spokeswoman Brooke Schulz said.
She added that the company has been meeting with the FCC weekly "to seek their guidance as to how to implement the approaching Aug. 29 cutoff date."
The division of Time Warner Inc. said in its FCC filing that all customers have already been adequately informed about the risk of losing 911 service in a power outage — the primary issue for cable-based VoIP services — and that all have already acknowledged that risk.
Some VoIP users have expressed anger on Web forums at what they perceive as a heavy-handed approach by the FCC, while others have mistakenly seen the disconnection warnings as an arbitrary policy adopted by their service providers.
Compared with many vague government pronouncements, the wording of the FCC order is clear-cut on the disconnections, which could create a situation where some VoIP users suddenly find themselves with no phone service at all during an emergency rather than a functioning phone with inferior 911 service.
The FCC declined to say how it might enforce or check up on compliance with the order, which originally called for disconnections in late July before the agency pushed the deadline to Aug. 29. The agency also declined to discuss whether it might allow another temporary reprieve.
Unlike the traditional telephone network, where phone numbers are associated with a specific location, VoIP users can place a call from virtually anywhere they have access to a high-speed Internet connection.
That "roaming" flexibility, while generally viewed as a benefit, can make it more complex to connect VoIP accounts to the computer systems that automatically route 911 calls to the nearest emergency dispatcher and instantly transmit the caller's location and phone number to the operator who answers the call.
As a result, most VoIP providers have only been able to offer a watered-down version of 911 service that often directs emergency calls to a general administrative phone number at a local public safety office. In many cases, those lines are not staffed by emergency operators, and some may even play only a recording or go unanswered, particularly during non-peak hours.
In addition, while traditional phone lines generally keep working during a blackout, VoIP users might not be able to dial 911 during a power outage because the high-speed Internet modems, phone adapters and personal computers needed for VoIP calling rely on electrical outlets and batteries.
Cable-based VoIP services have avoided the roaming issue by tying each phone number to a specific location and emergency dispatch center.
But VoIP providers who allow their customers to use their numbers in multiple locations face major challenges. They need to adopt a technology that will patch their customers into a disparate national patchwork of 911 call-routing systems and databases. That means they must reach an interconnection agreement with each of the more than 1,000 local phone companies who maintain and operate those 911 systems.