Abstract: A sensing and regulating apparatus for use with a tool such as a welding torch guided along a bevel, an oxygen cutting head, a chisel, a milling cutter, or a nibbling machine, comprises an optical apparatus projecting a light ray on a reference line where it delineates a spot which is diffused particularly toward a receiver consisting of elements sensitive to light. The spot of light falling on the receiver supplies two adjustment signals according to its position and its width. These signals are used to control elements carrying the optical apparatus so that the apparatus continually follows the reference line and so that it always remains at the same distance from the reference line. The movements of the optical apparatus control the associated working tool so that its path is equal, or homothetic, to that of the optical apparatus as a result of the reference line.