The invention relates to an imaging device for imaging a long object. The lock assembly draws the bed door down into proper contact with the door seal, as well as, securely locking the bed doors in their vertical closed position. The system also includes a filter that translates time-domain measurements of off-axis wafer surface gauge and the backplane gauge into space-domain measurements. From these mobile stations, a mobile station to which a transmission opportunity is assigned, is determined. The housing may be modular, including tabs on one component that are plastically deformed to engage a lip on another component.