Abstract: An apparatus including a source of a coherent light beam of low divergence for quickly and simultaneously establishing a plurality of reference lines or planes for use in leveling, squaring, plumbing, and other alignment functions and for controlling the operation of construction equipment is disclosed. The apparatus includes feet for supporting the housing on a surface, the feet being attached to the housing through an alignment and leveling device that permits adjustment of the orientation of the housing relative to the surface. The alignment and leveling device may be controlled in part by a pair of level vials which, when the feet support the housing on a substantially horizontal surface, have substantially horizontal axis that are perpendicular to one another. The level vials actuate a motor drive servomechanism that adjusts that housing relative to the surface until the axis of each level vial is horizontal.

Abstract: A comparison circuit for use in an apparatus including a source of a coherent light beam of low divergence for quickly and simultaneously establishing a plurality of reference lines or planes for use in leveling, squaring, plumbing, and other alignment functions and for controlling the operation of construction equipment is disclosed.The present invention is a circuit that finds particular utility in automatically adjusting the orientation of the tool. More particularly the present invention is a circuit for comparing the amplitude of a first alternating current signal to the amplitude of a second alternating current signal, such signals being in phase with one another and having the same frequency.