Human Factors Criteria for the Design and Acquisition of ... - FAA

Keyboards June 2004Exhibit 9.10.3.b Overshoot areaOvershoot area9.10.4 Key action. Keys should use an elastomer actioninstead of a linear spring or snap action. [Source: Akagi,1992; Brunner & Richardson, 1984]Additional information. Performance is higher with anelastomer action than a linear spring or snap action keymechanism. Although keys with linear spring action leadto lower errors and higher speed than snap action,elastomer action outperforms both linear spring and snapaction in performance and preference. [Source: Akagi, 1992;Brunner & Richardson, 1984]• 9.10.5 Key displacement. Vertical displacement of thekeys shall be between 1.3 to 6.4 mm (0.05 to 0.25 in), withpreferred displacement of 2.0 to 4.0 mm (0.08 to 0.15 in)for normal data entry tasks. [Source: ANSI, 1988; Ilg, 1987;Kinkead & Gonzalez, 1969; NUREG 0700, 2002; Radwin & Jeng,1997; Radwin & Ruffalo, 1999]Additional information. Displacements of between 2.0 and4.0 mm (.08 and .16 in) produce the highest text entry rateswith the lowest errors. Increasing key travel decreases keyforce, which is associated with higher carpal tunnelpressure. However, displacements of .7 to 1.6 mm (.03 to.06 in) are acceptable for data entry that is not continuous.[Source: ANSI, 1988; Ilg, 1987; Kinkead & Gonzalez, 1969; NUREG0700, 2002; Radwin & Jeng, 1997; Radwin & Ruffalo, 1999]9.10.6 Key rollover. Keyboards should have n-keyrollover. [Source: Kallage, 1972; NUREG 0700; 1981]Additional information. N-key rollover stores the keyspressed and allows them to be processed in the order thatthey were activated after the other key is released. N-keyrollover can minimize errors and slow downs for highspeeddata entry. [Source: Kallage, 1972]9-29