Updated

AT&T Inc. will start selling home automation and security services nationwide, taking on incumbents led by Tyco International Ltd.'s ADT.

The installations and services will be sold in AT&T stores, starting with a trial this summer in Dallas and Atlanta.

Several of AT&T's competitors, including cable TV company Comcast Corp. and phone company Verizon Communications Inc., have ventured into the home automation and security field. Dallas-based AT&T is showing more ambition with its stated goal of selling nationwide, rather than sticking to its landline service territory, as Verizon does.

Steven Winoker, an analyst at Sanford Bernstein, said about 23 percent of U.S. homes have security systems, so there's plenty of room to grow. Even fewer have automation systems for controlling appliances, lights, heating and cooling.

The biggest player in the field is ADT, but it has only 25 percent of the market. Many smaller companies make up the rest, according to Winoker.

It's a very profitable business, Winoker said, but it's not big enough to significantly affect the earnings of a company of AT&T's size even if it's successful, given that it's a relatively small market.

AT&T's technology comes from Xanboo, a company it bought in late 2010. Its central control panel can connect wirelessly with cameras, thermostats, appliance controls, lights and sensors for doors, windows, smoke and carbon monoxide. Through the panel, home owners can then control their home from their cellphones.

It's highly recommended that the control panel is connected to wired broadband, but it doesn't have to be service through AT&T, said Glenn Lurie, AT&T's president of emerging devices. As a backup, the panel can connect to AT&T's wireless data network.

AT&T didn't say what its services would cost.

AT&T made its announcement on the eve of the U.S. cellphone industry's annual trade show, which starts Tuesday in New Orleans.