Is ADT Owned By AT&T?

In 1909, American Telephone & Telegraph Company took ownership of both Western Union and ADT, making it their parent company (AT&T). Between the years 1910 and 1930, ADT started expanding into other markets, such as fire and security alarms, although it maintained its independence from AT&T's Holmes alarm business during this time. In the 1960s, ADT changed its status to that of a publicly listed business.