target at the end of the projectile's time of flight, adding in corrections for gravity, relative wind, the magnus effect of the spinning projectile, and parallax, the latter compensation necessary because the guns themselves were widely displaced along the length of the ship. Lead angles and corrections were added to the LOS data to generate the line-of-fire (LOF) data. The LOF data, bearing and elevation, as well as the projectile's fuze time, was sent to the mounts by synchro motors, whose motion actuated hydraulic servos with excellent dynamic accuracy to aim the guns. Once the system was "locked" on the target, it produced a continuous fire control solution. While these fire control systems greatly improved the long-range accuracy of ship-to-ship and ship-to-shore gunfire, especially on heavy cruisers and battleships, it was in the anti-aircraft warfare mode that the Mark 1 made the greatest contribution. However, the anti-aircraft value of analog computers such as the Mark 1 was greatly reduced with the introduction of jet aircraft, where the relative motion of the target became such that the computer's mechanism could not react quickly enough to produce accurate results. Furthermore, the target speed, originally limited to 300 knots by a mechanical stop, was twice doubled to 600, then 1,200 knots by gear ratio changes. The design of the postwar Mark 1A may have been influenced by the Bell Labs Mark 8, which was developed as an all electrical computer, incorporating technology from the M9 gun data computer as a safeguard to ensure adequate supplies of fire control computers for the USN during WW2. Surviving Mark 1 computers were upgraded to the Mark 1A standard after World War II ended. Among the upgrades were removing the vector solver from the Mark 1 and redesigning the reverse coordinate conversion scheme that updated target parameters. The scheme kept the four component integrators, obscure devices not included in explanations of basic fire control mechanisms. They worked like a ball–type computer mouse, but had shaft inputs to rotate the ball and to determine the angle of its axis of rotation. The round target course indicator on the right side of the star shell computer with the two panic buttons is a holdover from WW II days when early tracking data and initial angle–output position of the vector solver caused target speed to decrease. Pushbuttons slewed the vector solver quickly. See also Ship gun fire-control system Admiralty Fire