Mirrorless cameras and dSLTs use LCD or electronic viewfinders. Electronic viewfinders are used in digital still cameras and in video cameras. These "technical cameras" have separate viewfinders and rangefinders for faster handling. These viewfinders were fitted to inexpensive cameras. Olympus has four available add-on hotshoe viewfinders. The cameras were equipped with CPS tubes, had electronic viewfinders and a 3 lens turret. Such viewfinders were integrated into box cameras, and fitted to the side of folding cameras. To get the advantage of both optical and electronic viewfinders some cameras have hybrid viewfinders. The optical viewfinders provided with some video and digital cameras are not safe. Examples include small high-resolution displays such as those found in projectors or viewfinders. Some special purpose cameras do not have viewfinders at all. These displays are used in LCD Camera viewfinders and other industrial applications. It also removes the need to have separate viewfinders for different lens focal lengths. Reflex viewfinders, both twin-and single-lens, had been used with earlier cameras using plates and rollfilm. With the exception of the "P" spec camera, all viewfinders are completely interchangeable.