He married Phoebe in August 1916. They had two sons: Richard Davis Bush and John Hathaway Bush. Bush accepted a job with Tufts, where he became involved with the American Radio and Research Corporation (AMRAD), which began broadcasting music from the campus on March 8, 1916. The station owner, Harold Power, hired him to run the company's laboratory, at a salary greater than that which Bush drew from Tufts. In 1917, following the United States' entry into World War I, he went to work with the National Research Council. He attempted to develop a means of detecting submarines by measuring the disturbance in the Earth's magnetic field. His device worked as designed, but only from a wooden ship; attempts to get it to work on a metal ship such as a destroyer failed. Bush left Tufts in 1919, although he remained employed by AMRAD, and joined the Department of Electrical Engineering at Massachusetts Institute of Technology (MIT), where he worked under Dugald C. Jackson. In 1922, he collaborated with fellow MIT professor William H. Timbie on "Principles of Electrical Engineering", an introductory textbook. AMRAD's lucrative contracts from World War I had been cancelled, and Bush attempted to reverse the company's fortunes by developing a thermostatic switch invented by Al Spencer, an AMRAD technician, on his own time. AMRAD's management was not interested in the device, but had no objection to its sale. Bush found backing from Laurence K. Marshall and Richard S. Aldrich to create the Spencer Thermostat Company, which hired Bush as a consultant. The new company soon had revenues in excess of a million dollars. It merged with General Plate Company to form Metals & Controls Corporation in 1931, and with Texas Instruments in 1959. Texas Instruments sold it to Bain Capital in 2006, and it became a separate company again as Sensata Technologies in 2010. In 1924, Bush and Marshall teamed up with physicist Charles G. Smith, who had invented a device called the S-tube. This enabled radios, which had previously required two different types of batteries, to operate from mains power. Marshall raised $25,000 to set up the American Appliance Company on July 7, 1922, to market the invention, with Bush and Smith among its five directors. The venture made Bush wealthy, and the company, now known as Raytheon, ultimately became a large electronics company and defense contractor. Starting in 1927, Bush constructed a differential analyzer, an analog computer that could solve differential equations with as many as 18 independent variables.