In Norden's version of the system, the bombardier first looked up the expected time it would take for the bombs to fall from the current altitude. This time was set into a countdown stopwatch, and the bombardier waited for the target to line up with a crosshair in the telescope. When the target passed through the crosshair, the timer was started, and the bombardier then rotated the telescope around its vertical axis to track the target as they approached it. This movement was linked to a second crosshair through a gearing system that caused the second to move twice as fast as the first. The bombardier continued moving the telescope until the timer ran out. The second crosshair was now at the correct aiming angle, or "range angle"; the bombardier waited for the target to pass through the second crosshair to time the drop.