spacious in comparison with the T-54 because of the thinner armour and has different locations for some equipment. The general layout, with transverse mounting of the engine, is the same. Driver's compartment The driver's compartment is located on the left hand side of the front of the hull. The driver's seat is moved forward and to the left in comparison with its location in the T-54. The compartment is equipped with a single-piece hatch cover opening to the left and two periscopic vision devices. One of them can be replaced by the TVN-1 infrared vision device which is operated together with the infrared headlamp (active night vision), which is mounted on the right track board. A fire-fighting equipment signal panel and a spare parts case are also located in the driver's compartment. Turret The open-topped box-type welded turret has a ball-bearing race ring 1850 mm in diameter. The turret rear can be removed, which makes replacement of the guns easier. The turret can be covered in the travelling position by a tarpaulin which has 16 plexiglass windows. To aim the guns, base data such as the target's speed, direction and range must be entered into the sighting system by the sight adjuster, who sits to the left of the guns at the rear of the turret. The target's speed and direction is determined by visual estimation, while range can also be estimated visually or with the rangefinder. The upper front of the turret has two small ports with armoured covers meant for collimators of the sight. To fire the guns, the breeches must first be opened. The left and right loaders, located in the forward part of the turret on both sides of the main armament, load clips into the magazines of their respective weapons. The loaders' travel seats should be stowed in clamps on the turret sides before opening fire. The gunner, seated on the left hand side in the middle of the turret, aims ("lays") the gun and opens fire using an electric trigger, which fires both barrels, or two-foot pedals, which can fire either barrel independently. If manual mechanical backup gunlaying is used instead of electro-hydraulic drive, three crew members instead of two should work with the sight. The commander, who sits on the right hand side in the middle of the turret, lays the gun in azimuth, the gunner in elevation and the sight adjuster enters