DeanneLong650

ADT incorporated into Western Union in 1901. ADT separated its messenger business from its main signaling business at this time. In 1909, Western Union and ADT came under the control of AT&T. ADT began to expand into new areas such as fire alarms and burglar alarms between 1910 and 1930, but was kept separate from AT&T's Holmes alarm business. ADT became a publicly owned company in the 1960s