US Patent 10272872 Belt assembly allowing payout measurement

A belt assembly includes a belt, a first sensor and a second sensor. The belt has a webbing and a plurality of markers distinct from the webbing and fixed thereto. The markers are equally spaced a first longitudinal distance thereon in a longitudinal direction. The first sensor and the second sensor each have an associated detection field directed toward the belt and responsive to the markers in the fields. The second sensor is a second longitudinal distance from the first sensor differing from the first distance.