ineffective. Contractor saws were originally designed to be somewhat portable, often having wheels, and were frequently brought to job sites before the invention of smaller bench-top models in the early 1980s. Contractor saws are heavier than bench-top saws, but are still lightweight when compared to cabinet saws. Their larger size and greater power allows them to be used for larger projects and allows them to be more durable, accurate, and longer-lasting then bench-top saws. Cabinet Cabinet table saws are heavy, using large amounts of cast iron and steel, to minimize vibration and increase accuracy. A cabinet saw is characterized by having an enclosed base. Cabinet saws usually have induction motors in the range, single-phase, but motors in the range, three-phase, are common in commercial/industrial sites. For home use, this type of motor typically requires that a heavy-duty circuit be installed. The motor is enclosed within the cabinet and drives the blade with one or more parallel V-belts, often "A" belts as "A" belts may be ganged without having to be specially selected (otherwise, specially selected sets of light-duty "4L" belts are used). Cabinet saws offer the following advantages over contractor saws: heavier construction for lower vibration and increased durability; a cabinet-mounted trunnion (the mechanism that incorporates the saw blade mount and allows for height and tilt adjustment); improved dust collection due to the totally enclosed cabinet and common incorporation of a dust collection port. Cabinet saws are designed for, and are capable of very high duty-cycles, such as are encountered in commercial/industrial applications. Where some of the advantages of a cabinet saw are desired in a home shop application, so-called "hybrid" saws have emerged to address this need. Cabinet saws have an easily replaceable insert around the blade in the table top allowing the use of zero-clearance inserts, which greatly reduce tear out on the bottom of the workpiece. It is common for this type of saw to be equipped with a table extension that increases ripping capacity for sheet goods to . These saws are characterized by a cast iron top on a full-length steel base, generally square in section, with radiused corners. Two miter slots ( wide on the largest saws) are located parallel to the blade, one to the left of the blade and one to the right. American-style cabinet saws generally follow the model of the Delta Unisaw, a design that has evolved since 1939. Saws