Abstract: A hitch control unit for use in a tractor comprises a housing that defines an arcuate surface having a tangentially extending slot. An arm extending through the slot is rotatably mounted in the housing and connected to a transducer to produce a signal indicative of the position of the arm along the slot. A stop movably mounted in the housing defines a reference position for the arm along the slot, and a finger-actuated wheel rotatably mounted in the housing allows the position of the movable stop along the slot to be adjusted. The wheel has an internally screw threaded bore and is mounted in the housing for rotation about an axis that extends parallel to the slot and the adjustable stop is connected to an arcuate rack in screw threaded engagement with the bore in the wheel.