An apparatus for determining a level of a liquid in a tank is provided. The safety means comprises an electronic control unit for the authentication of an authorized user and the control of a safety mechanism. A deflector located below the gap deflects scrap sod and defective sod rolls onto the cut portion of the sod field, rater than onto the uncut portion, so that the scrap sod deflected onto the field will not interfere with the next pass of the cutting head. Seed and barrier layers are deposited on the trench and the via. The contents of the display buffer are provided to a display at a display update rate to show a composite of all waveform images representing the electrical signal. At least one of the upper paper guide and the lower paper guide is supported swingably during printing operation.