NEW YORK (AP) — 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.