Skip to Content

T-Mobile Will Now Let Phone Numbers Ring on Any Mobile Device

Inside A T-Mobile US Inc. Store Ahead Of Earnings FiguresInside A T-Mobile US Inc. Store Ahead Of Earnings Figures
Employee assist customers at a T-Mobile US Inc. store in Chicago, Illinois, U.S., on Friday, Oct. 21, 2016. T-Mobile US Inc. is scheduled to release earnings figures on October 24. Photographer: Daniel Acker/Bloomberg via Getty ImagesDaniel Acker — Bloomberg via Getty Images

T-Mobile famously disconnected mobile phones from two-year service contracts and then broke the link between phones and the cellular network with Wi-Fi calling. On Wednesday, the pioneering carrier announced a beta project to go even deeper, separating phones from phone numbers.

Dubbed Digits, the new project in some ways resembles services from Google (GOOGL), Skype (MSFT), and others that allow users to make and receive calls on multiple devices with one number. But T-Mobile’s solution, which will be rolled out to all customers early next year, uses the core phone network and doesn’t rely on workarounds that mess up caller ID and other telephony functions.

Beta testers will be able to assign their T-Mobile number on up to five devices—including phones, tablets and personal computers—to make and receive calls and texts. Users will also be able to assign up to five numbers to any one device. And those devices don’t have to be on T-Mobile’s network–users can assign their Digits numbers to phones getting service from Verizon (VZ), Sprint (S), or AT&T (T). Everything will be controlled from the “My T-Mobile” section of T-Mobile’s web site, and eventually via a related app.

T-Mobile (TMUS) customers can sign up for the beta test starting on Wednesday. During the test the service will be free, but some fee is likely once Digits is available to all T-Mobile customers, T-Mobile chief operating officer Mike Sievert tells Fortune.

“Expect it will be simple and it will be disruptive,” Sievert says without giving away the details.

T-Mobile, the nation’s third-largest carrier, has gained a reputation for bucking industry conventions under CEO John Legere. So far Legere’s “un-carrier” strategy has worked, as the company has doubled its customer base and nearly quadrupled its stock price. Lately, that success prompted a host of M&A speculation that other wireless companies, cable companies, or even big tech companies might want to buy T-Mobile from majority-owner Deutsche Telekom.

Get Data Sheet, Fortune’s technology newsletter.

With the Digits project, the separation of phone numbers from physical devices means that call histories, voice mails, past text messages, and contact lists can be accessed from anywhere as well. That may come in handy for businesses that want to assign numbers to employees’ mobile phones and have them access contact lists without giving up control of the data, Sievert says.

Digits also breaks the connection between a phone number and the SIM card in a phone, making it much easier to have multiple phones on one account. That could prompt people to use a greater diversity of phone form factors, Sievert thinks. “You could have different devices for different aspects of your lifestyle,” he says. “This is my itty bitty phone for nights out on the town. This is my waterproof phone for the beach.”

Still, that vision may be a stretch in an age when calling—and increasingly even texting—have been overtaken by more app-based communications platforms like Snapchat, Instagram (FB), and WhatsApp.

And T-Mobile says it had to re-engineer its calling and identity management systems, with multiple pending patents covering the technology. So the company is unlikely to be sharing the technology with other carriers.

“There are a ton of patents around this,” T-Mobile chief technology officer Neville Ray tells Fortune. “I’m not saying others couldn’t do it. It’s going to take them some time.”

That may give T-Mobile an advantage in wooing customers, but it also prevents the notion of unconnected numbers and devices from becoming ubiquitous.

The goal was to create a simple service and hide the technological reshuffling of core telephone systems “There’s a lot of technology behind the scenes that we are not asking the customer to solve or manage,” Ray explains.

For a look at one of Legere’s early marketing efforts at T-Mobile, watch:

On most devices, Digits users will have to make calls and texts with an app or via a web browser. Only Samsung’s Galaxy S6, S7, and Note 5 devices have native support for Digits built into the phone dialing software, though T-Mobile said it is working to add that level of integration to other manufacturers phones.

One potential hitch in the early going is that Digits is not compatible with Apple’s (AAPL) popular iMessage network for text messaging. A Digits user with an iPhone or iPad would have to turn off iMessage functionality to get all of the T-Mobile features, such as the synched texting history on every device. T-Mobile is talking to Apple (AAPL) about adding full compatibility with iMessage as well as iPhone dialer integration. Apple already mimics some of the Digits features via what it calls iCloud wi-fi calling.

Still, T-Mobile is pressing for greater integration with Digits. “We’d love to see it,” Sievert says. “These are very close partners of ours.”