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AT&T is nearly ready to launch a feature that will allow a customer’s smartphone, tablet and other devices to share a single phone number.

The feature, now called NumberSync, is a key to making it more attractive for customers to own multiple devices with built-in wireless connections, just as it was important to offer shared data plans.

As previously reported by Re/code, AT&T has been testing the underlying technology, code-named Cascade, since at least last year. It was developed in part at the company’s Foundry incubator in Palo Alto, Calif.

“This is really a first in the industry that we are giving customers the ability to do this,” AT&T Mobility CEO Glenn Lurie told Re/code.

AT&T said it expects to launch NumberSync on an initial device “fairly soon” with additional devices coming later this year. Many existing smartphones will be able to support the feature through a software upgrade; the company’s goal is to work with all manufacturers to support the feature going forward in both phones and connected devices, such as tablets and watches.

There won’t be a separate charge to share one number, but AT&T already charges a per-device fee, typically $5 or $10, for each device that connects to a shared data plan.

Because NumberSync is network-based, AT&T says the technology will work even if the primary phone is off and doesn’t require any devices to be near one another. Apple, for example, has features that allow users to answer calls on their Mac or tablet, but require the device to be on the same network.

Lurie has said he expects that wearables with cellular connections will become the norm, though he acknowledged at last week’s Code/Mobile that uptake of such devices has been slower than he had initially thought.

“For us to really have the wearable space explode … those devices have to work in concert with each other,” Lurie said.

Another place where NumberSync is likely to show up is in the connected car, Lurie said, noting that pairing smartphones to cars via bluetooth remains a complicated experience. Over time, NumberSync could also allow people to take calls on various devices in their home and office, Lurie said.