Work also started on a suitable gun-laying computer that could use electrical, as opposed to mechanical, inputs for pointing data. Bell Labs delivered an analog computer known as the M9 Director for this role. The M9 had four sets of outputs, allowing a single M9 to control four of the Army's standard 90 mm M1 guns. The entire system, including the M9, was demonstrated in complete form on 1 April 1942. A contract for over 1,200 systems arrived the next day. Bell also worked on their own microwave radar as a backup project.