Laser-controlled machines give the operator instant feedback on his cutting position. A laser transmitter, emitting a thin 360 degree rotating beam, provides a constant grade reference to a receiving system mounted on the blade of the machine. The receiver detects the laser signal and then indicates whether the cutting edge is above, below, or on grade. For manual operation, the receiver uses flashing lights to display grade information. The receiver can also be rigged to provide automatic operation, that is, control the machine's hydraulic system to respond to grade information.
Although similar to laser devices used in setting elevations for construction, the transmitter and receiver used for machine control have some special features. The transmitter range usually exceeds 1,000 feet in radius, making it less likely that the machine will run out of the transmitter range. Also, manufacturers have developed a limiting switch that warns the operator if elevation changes too much. The switch helps to assure correct laser beam elevation throughout the day. The receiver is typically packaged into a machine control system that provides two functions: it receives the laser beam, and it informs the operator of the position of the cut. Another useful feature lets the operator know if the machine moves outside the transmitter range.