File:Low Level Bombsight Mark III computor.jpg

English: The Low Level Bombsight Mk. III consisted of two parts, the sight head, and the computor, shown here.

The computer consists primarily of two parts, the large white cylinder visible through the perspex (plexiglass) window on top, and the moving pointer just visible to the left of the middle pair of (rusty) screws. The bomb aimer rotated the cylinder to select the type of bomb they were using and the aircraft's altitude, read against the pointer at the left end of the window. The aircraft's airspeed was dialed in using the knob on the upper right corner, moving the pointer back and forth across the face of the cylinder. The intersection of the (virtual) lines extending from the two pointers can be read against the lines on the cylinder to read the range, the distance the bombs will travel forward while they fall.

A simple mechanical calculator inside the device converts this to the angular velocity of an object at that distance from the aircraft, which was used to drive the sight head's display. The output was an electrical current which was connected to the sight head through a cable screwed onto the fitting in the upper left.