Its scissor mechanism gives the S-board 840 a light keystroke. Its compact format prevents strain because the mouse is much easier to reach. A compact keyboard does not have a numeric pad. For this reason, the mouse can be placed closer to the keyboard. Research has shown that 90% of keyboard users seldom if ever use the numeric pad. Working with a compact keyboard results in greater comfort because it reduces the reaching distance to the mouse (Cook, C., et al., 1998). This puts less strain on the shoulder and forearm. Dark letters on a light background make them easier to read (ISO 9241), and contribute to increased productivity (Snyder, 1990).