pointing device
A pointing device is an input interface that allows a user to input data to a computer using physical gestures - point, click, and drag - for example, by moving a hand-held mouse across the surface of the physical desktop and activating switches on the mouse. Movements of the pointing device are echoed on the screen by movements of the pointer (or cursor) and other visual changes.
While the most common pointing device by far is the mouse, many more devices have been developed.
The mouse is the most common form of pointing device for computers. It is made up of three keys and a scrolling wheel for easy access in surfing through a document or file. An indication of the mouse in use is through the display of a pointer on the screen's interface. With the sight of you, one is able to pinpoint where the cursor is (or in some cases, hand gesture) and is able to make whatever changes necessary to their document or basically given the opportunity to operate the computer in a way that would require fine motor skills.
The shape of some mice make them unsuitable for a left-handed person, but there are some mice specifically designed for left-handed users. Resting the fingers on the keys on a mouse should not activate the key. Tactual and auditory feedback should be provided on activation of a key.
The user should have the ability to modify the speed of movement of the cursor, the distance moved by the cursor and the double-click interval.
The shape of some mice make them unsuitable for a left-handed person, but there are some mice specifically designed for left-handed users. Resting the fingers on the keys on a mouse should not activate the key. Tactual and auditory feedback should be provided on activation of a key.
The user should have the ability to modify the speed of movement of the cursor, the distance moved by the cursor and the double-click interval.
Alternatives to the standard mouse
- Trackball
- Joysticks
- Mouse control using a switch and any reliable body part movement
- Mouse control via head movement only
- Mouse control via eye movement only
- Mouse control via sip/puff mouth actions
ALTERNATIVE POINTING DEVICES
ROLLER OR TRACKBALL
Roller or trackballs consist of a small ball rotating freely in a fixed bed containing sensors to detect rotation of the ball about two axes. These devices are sometimes incorporated in public access terminals since, unlike a mouse, they do not need a surface to work on and they are more resistant to vandals.
People with a mobility impairments use trackballs as an alternative input device. The control surface of a trackball is easier to manipulate and the buttons can be activated without affecting the pointer position. Some physically impaired users find trackballs easier since they only have to move their thumb relative to their hand, instead of moving the whole hand, while others incur unacceptable fatigue of the thumb. Elderly people sometimes have difficulty holding a mouse still while double-clicking; the trackball allows them to let go of the cursor while using the button. However trackballs can be problematic for users with poor manual dexterity, and they have a tendency to be slightly slower than a mouse.
People with a mobility impairments use trackballs as an alternative input device. The control surface of a trackball is easier to manipulate and the buttons can be activated without affecting the pointer position. Some physically impaired users find trackballs easier since they only have to move their thumb relative to their hand, instead of moving the whole hand, while others incur unacceptable fatigue of the thumb. Elderly people sometimes have difficulty holding a mouse still while double-clicking; the trackball allows them to let go of the cursor while using the button. However trackballs can be problematic for users with poor manual dexterity, and they have a tendency to be slightly slower than a mouse.
Supplementary switch: Many people find that the most difficult part of using a mouse is holding it steady while pressing the button. One solution is to consider adding an external switch to act as the left or right mouse button, or both.
JoystickSpecialist joysticks: classed as an assistive technology pointing device, are used to replace the computer mouse for people with fairly severe physical disabilities by pluging into the USB port and controlling the mouse pointer.They can be of either displacement or force type. Displacement joysticks are by far the most common type and are what most people envisage when they consider joysticks. Force applied to the handle causes it to move over several degrees (usually between 20 and 30). This movement is detected and converted to an electrical signal by a potentiometer or a non-contacting technology device. Displacement joysticks are better for positioning accuracy than positioning speed, but it is essential that they return to the default position (usually the centre) when released. Force sensitive or "stiff stick" joysticks use strain gauges to convert applied force into a proportional electrical output. Typically a movement of less than 1mm is needed to achieve full scale output. Force joysticks pose particular problems for visually impaired and dexterity impaired people. Joysticks are often useful to people with athetoid conditions, such as cerebral palsy, who find them easier to grasp than a standard mouse. Miniature joysticks are also available for people with conditions involving muscular weakness such as muscular dystrophy or motor neurone disease.
Head Operated: For some people whose only, or most reliable, movement is with their head, a head operated mouse may be the best solution. It translates the movements of a user's head into directly proportional movements of the computer mouse pointer. Head operated mice are now quite small and compact units which attach to the front of a desktop or laptop computer screen, and may also be used with many communication devices.
Head operated mice function by a wireless optical sensor which uses infrared light to track a small disposable target that is placed on the user's forehead or glasses.
Fatigue can be an issue when a lot of keystrokes are required in order to accomplish a task however head operated mice can offer accurate mouse operation.
Head operated mice function by a wireless optical sensor which uses infrared light to track a small disposable target that is placed on the user's forehead or glasses.
Fatigue can be an issue when a lot of keystrokes are required in order to accomplish a task however head operated mice can offer accurate mouse operation.
Eye tracking devices can be a powerful alternative for individuals with no control, or only limited control, over their hand movements.
A camera mounted on a computer monitor is focused on one eye. The available software processes the camera image to determine where the user is looking (gaze point), and the cursor is then placed at the gaze point. "Mouse clicks" are done with either a slow eye blink, eye gaze or a supplementary switch. Special software allows the person to type, and may include word-completion technology to speed up the process. These systems can be very costly.
Further information: http://www.tiresias.org/research/guidelines/pointing_devices.htm
A camera mounted on a computer monitor is focused on one eye. The available software processes the camera image to determine where the user is looking (gaze point), and the cursor is then placed at the gaze point. "Mouse clicks" are done with either a slow eye blink, eye gaze or a supplementary switch. Special software allows the person to type, and may include word-completion technology to speed up the process. These systems can be very costly.
Further information: http://www.tiresias.org/research/guidelines/pointing_devices.htm