Suchergebnisse

The standard typewriter keyboard serves as a model for keyboards of teletypewriters, desk calculators, consoles, computer keysets, cash registers, etc. This man-machine interface should be designed to allow high-frequency, error-free operation with the least possible strain on the operator. This paper discusses several feasible biomechanical improvements of the keyboard. Some experimental findings are described which support the following design concepts: (1) the keys should be arranged in a "hand-configured" grouping to simplify the motion patterns of the fingers; (2) the keyboard sections allotted to each hand should be physically separated to facilitate the positioning of the fingers; and (3) the keyboard sections allotted to each hand should be declined laterally to reduce postural muscular strain of the operator.

Describes a simple way to familiarize blind students with the layout of a typewriter keyboard: Brailled letters of the alphabet were Thermoformed and glued to ¾ "-square ceramic tiles that had a Velcro backing. The tiles could be in turn positioned along strips of Velcro to simulate the position of typewriter keys. Once students had gained familiarity with this layout, their knowledge was tested by having them detect which tiles were missing or incorrectly positioned.

This study examines the relationship between forearm EMGs and keyboard reaction forces in 10 people during keyboard tasks performed at a comfortable speed. A linear fit of EMG force data for each person and finger was calculated during static fingertip loading. An average r2 of .71 was observed for forces below 50% of the maximal voluntary contraction (MVC). These regressions were used to characterize EMG data in force units during the typing task. Averaged peak reaction forces measured during typing ranged from 3.33 N (thumb) to 1.84 N (little finger), with an overall average of 2.54 N, which represents about 10% MVC and 5.4 times the key switch make force (0.47 N). Individual peak or mean finger forces obtained from EMG were greater (1.2 to 3.2 times) than force measurements; hence the range of r2 for EMG force was .10 to .46. A closer correspondence between EMG and peak force was obtained using EMG averaged across all fingers. For 5 of the participants the force computed from EMG was within ±20% of the reaction force. For the other 5 participants forces were overestimated. For 9 participants the difference between EMG estimated force and the reaction force was less than 13% MVC. It is suggested that the difference between EMG and finger force partly results from the amount of muscle load not captured by the measured applied force.

These studies demonstrate the inferiority of alphabetically organized keyboards as compared with a randomly organized keyboard and the standard Sholes (qwerty) keyboard. Use of the alphabetic keyboard requires considerable mental processing; the novice is faced with a trade-off between mental processing and visual search, and this makes different keyboard layouts equivalent. Comparison of different keyboard layouts by computer simulation of expert typing shows surprisingly little effect of keyboard arrangement for a wide class of keyboards. Performance with some alphabetical layouts is quite slow, but with others, it is within 2% of the speed achieved when using the Sholes keyboard. Performance with the Dvorak keyboard is only improved by about 5% over performance on the Sholes keyboard. The conclusion is that it is not worthwhile to use alphabetic keyboards for novice typists, nor to change to the Dvorak layout for experts. Keyboards can probably be improved, but only through radical redesign of the present physical key configuration.