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T-Mobile Digits frees your phone number from your phone

David Pogue
Tech Critic

T-Mobile, man. That company (TMUS) is just determined to mess with the traditional cellphone-carrier model.

This is the company that eliminated the two-year contract. That lets you stream all the music and video you want, without counting it against your data allotment. That eliminated international roaming charges.

And now, the company wants to give you another phone number.

It’s called T-Mobile Digits, a new service, currently in free beta testing for T-Mobile customers. The central idea is that Digits breaks the one-to-one bond between your phone number and your phone.

In so doing, Digits introduces all kinds of new flexibility—and complexity—into your digital life. They fall into one of two categories, which I’ll call “One to many” or “Many to one.”

When you sign up for the program, you can choose one of those categories, or both of them. (Told you this was going to involve some complexity!)

One to many

When you sign up for this option, your one T-Mobile number rings all your phones—even phones from Verizon (VZ), Sprint (S), or AT&T (T), and even WiFi-only devices like tablets! The idea is that you can now take and make calls, and send or receive messages, from whichever phone you have with you.

(If you’re hoping to include a non-smartphone in your arsenal, T-Mobile will send you an SIM card for it. Which means you’ll have to replace the phone’s existing SIM card. Which means it will have only one phone number. Which means you won’t be able to use the “many to one” feature described below. Did I mention that this all gets a little complex?)

When someone dials your one T-Mobile number, all of your associated gadgets ring at once. When you pick up one to answer it (or decline it), all the other devices stop ringing.

All your phones ring simultaneously—even non-T-Mobile ones.

So why is this useful? Well, if you race out of the house and forget your phone, no problem! You can borrow a phone, or you can use the Digits website. You can still get your calls and texts.

Or maybe you want to take a cheap ratty old feature phone with you running or rowing, instead of carrying your precious $700 smartphone. No sweat; now that ratty old feature phone can get (and send) your calls and texts.

Heck, you could now treat cellphones like multiple extensions of a landline. You can keep one phone up by your bed, and another downstairs; pick up whichever one is handiest when someone calls or texts.

What’s cool is that you can access your calls, texts, and voicemail from any device. From a watch. From a WiFi tablet. From any computer, tablet, or phone in the world, via the Digits website.

Suddenly, any browser on earth is a cellphone you can use.

Many to one

The other Digits option is the reverse: That is, you can also get a second phone number for your one phone. You can give out Phone Number A to your personal contacts, and reserve Phone Number B for business use.

When people call your one phone, you’ll see on the screen whether they’ve called Number A or Number B, so you’ll know which voice to use when you answer it. (You wouldn’t want to pick up and say, “Hey there, sugar lips” when it’s your boss, now, would you?)

And what about placing a call? How do you choose which “line” to use?

Here’s where things start getting complicated. If you have a recent Samsung model (Galaxy S6 or S7 family, or Note 5), the dialer app includes a handy pop-up button that lets you choose the outgoing line.

Recent Samsung phones have multiple-line options built right in.

If you have any other phone, you have to use the T-Mobile Digits app to place your calls and send your texts. It, too, offers a pop-up switch that lets you choose the line.

On non-Samsung phones, the Digits app asks which number you want to use for dialing.

How is this not Google Voice?

Now. If you think all this sounds like Google Voice, you’re right. Google (GOOG, GOOGL) Voice also gives you a virtual number that also rings all your phones at once. And also lets you place calls from that virtual number from any device. And Google Voice is free, which T-Mobile Digits won’t be after the beta period. (T-Mobile hasn’t said what the monthly cost will be.)

Google Voice also offers a bunch of other cool features. You can specify which phones ring at which hours of the day (“Don’t ring this phone after 6 p.m.”, for example). You can record a different voicemail greeting for each caller in your Address Book. You can transfer a call from one phone to another in mid-call. You get written transcriptions of your voicemail, which is not always perfect but is always useful. (This feature seems to be available in the Digits app, but I couldn’t figure out how to turn it on.)

T-Mobile argues that Digits is better than Google Voice. For starters, you can keep using your existing T-Mo phone number. (Of course, you can always port your existing phone number to Google Voice, too.)

Moreover, you get “high-definition voice” (the enhanced audio quality available when you’re calling another T-Mo customer) using Digits. It’s a “real, carrier-grade call,” a rep told me; it’s not being routed through some Google computer.

On the other hand, just last week, Google Voice received its first big upgrade in five years, along with a promise from Google that its chronic neglect of Voice is over. (Funny about that timing, eh? Five years without a peep—then T-Mobile unveils Digits, and BOOM!)

The iPhone conundrum

It’s pretty cool that your one T-Mobile number can somehow ring non-T-Mobile phones.

If you have an iPhone, however, there’s a footnote concerning iMessages. (That’s Apple’s (AAPL) proprietary enhanced texting service, filled with additional features: no length limit; a “the other person is currently typing” indicator; “message read” indicators; synchronized texts across all your Apple products; easy file transfers; and so on.)

Most reviewers are reporting that you have to give up iMessages entirely—turn it off—in order to use Digits. Indeed, that’s what I said in my video, above.

The answer is actually more nuanced. Your iMessages still work—it’s just that they won’t show up on your other Digits devices. If you go for a run with your cruddy 2007 Samsung, you’ll miss any text messages people send to your iPhone, and messages you send from Messages on that iPhone won’t appear on any of your other Digits devices.

You have to turn off iMessages only if you want all your incoming text messages to appear in the Digits app, on all your devices.

Told you this was complicated.

The impossibility of a conclusion

So how do you review T-Mobile digits? It’s really tough, because we don’t yet know what it will cost.

And, of course, everybody’s different. Your life may be complicated enough that you’d welcome the Digits decoupling of phone number and phone. Or you may crave simplicity and wonder why anyone would want or need the Digits kind of flexibility.

For now, here’s what we can say: There are some small bugs; for example, if you reject an incoming call, it goes into your phone’s regular voicemail app—but if you let it ring through to voicemail, it goes to the Digits app’s voicemail. And, of course, that iPhone iMessages business is a drag.

Still, even in its free beta-test period, Digits does what it says it will do. If you’re a T-Mo customer who faces the Digits use cases (you want two lines; you want multiple phones with the same number), you’ll be pleased.

If you’re anyone else, there’s always Google Voice.

David Pogue, tech columnist for Yahoo Finance, welcomes non-toxic comments in the Comments below. On the Web, he’s davidpogue.com. On Twitter, he’s @pogue. On email, he’s poguester@yahoo.com. You can read all his articles here, or you can sign up to get his columns by email.