former American conglomerate corporation engaged mostly in automotive and aerospace engineering, energy development, and environmental improvement. It became part of AlliedSignal in 1985.

The company was incorporated in 1928 as the Signal Oil and Gas Company to continue the business of Signal Gas Company. Within a few months it became involved in the production side of the petroleum industry. It assumed the name Signal Companies, Inc., in 1968.

Over the years the company grew through acquisition into a highly sophisticated technological concern. In 1964 it entered the aerospace field by acquiring Garrett Corporation, which manufactured engines, control systems, and other aircraft and missile components used on nearly all U.S. commercial and military aircraft of the time. In 1975 the company acquired a controlling interest in UOP Inc. (formerly Universal Oil Products Company), which produced environmental control systems and provided technology for the petroleum-refining and petrochemical industries. Signal's other subsidiaries included Dunham-Bush, manufacturer of refrigerating and cooling equipment, Ampex Corporation, a manufacturer of audio and video, data-memory, and magnetic-tape products, and Wheelabrator-Frye, an engineering and construction concern.