The latest edition of the Apple Watch will at last fulfill the dreams of everyone who ever read Dick Tracy and wanted the hard-boiled detective’s two-way wristwatch radio. The Series 3 will have cellular connectivity, Apple chief operating officer Jeff Williams revealed at Tuesday’s product launch. And making a watch into a working cellphone is no easy feat.

As Williams explained, a watch that’s also a phone needs to include antenna, radio, power amplifiers, a sim card, and all the other tech that the designers of the company’s previous smartwatches didn’t have to worry about. All those new components take up space, and there can come point where it’s all more trouble than it’s worth.

“If it gets so big, it’s going to look like a house arrest bracelet, and you won’t want to wear it,” Williams observed.

The antenna of the Apple Watch is also its display.

But Apple showed some serious ingenuity in keeping the Series 3 at a manageable size. For instance, the watch’s display doubles as its antenna.

“Even with all these new features — all the stuff you have to put in for cellular — the case for Series 3 is the same size for Series 2,” said Williams. “The only difference is we extended the back crystal by the width of two sheets of paper.”

The inner workings of the Apple Watch

Williams called adding cellular connectivity the ultimate expression of the Apple Watch, making it possible for users to leave their iPhone at home and head to the beach or run an errand without having to lose touch with the world. Each Apple Watch will share the same number as the user’s iPhone.

“Now you have the freedom to go anywhere with just your Apple Watch,” said Williams. “This has been our vision from the very beginning.”

Photos via Apple