Abstract: A feederhouse on an agricultural combine. Having a first acoustic array having a first sounding board and acoustic sensor positioned beneath the front drum and feederhouse floor. A second acoustic array positioned behind the front drum and between the conveyor chain encircling the front and rear drums. The second acoustic array also has a second acoustic sensor and second sounding plate. The acoustic sensor detects the impact of a stone on the sounding plates. A signal is transmitted via a controller from the sensor to a solenoid controlling a stone trap door latch. When the door opens, a sled also rotates into contact with conveyor chain. This deflects any crop flow containing stones. To close the door, the feederhouse is raised and the door rotates into contact with the latch.

Abstract: The disclosure relates to an apparatus for controlling the position of a header relative to the ground surface, the apparatus including one or more pivotable shoes arranged to contact the ground and to move in dependence on changes in the ground contour. A further member secured to such a pivotable shoe includes a reflecting surface remote from the point of contact of the shoe with the ground surface. An emitter/receiver is spaced from the reflecting surface and connected to a control circuit whereby the position of the header relative to the ground may be measured by virtue of the position of the reflecting surface. The position of the header relative to the ground surface is then adjustable in dependence on the detected measurements, by means of various actuators associated with the apparatus.