Characteristics of Device Based Controls:

1. Trackball
2. Joystick
3. Graphic Tablet
4. Touch Screen
5. Light Pen
6. Voice
7. Mouse
8. Keyboard

1. Trackball

Trackball is a spherical object (ball) that rotates freely in all directions in its socket.Direction and speed is tracked and translated into cursor movement.

Advantages

• Direct relationship between hand and pointer movement in terms of direction and speed.
• Does not obscure vision of screen.
• Does not require additional desk space (if mounted on keyboard).

Disadvantages

• Movement is indirect, in a plane different from the screen.
• Indirect relationship between hand and pointer movement in terms of distance.
• Requires a degree of eye-hand coordination.
• Requires different hand movements.
• May be difficult to control.
• May be fatiguing to use over extended time.

2. Joystick

• A stick or bat-shaped device anchored at the bottom.
• Variable in size, smaller ones being operated by fingers, larger ones requiring the whole hand.
• Variable in cursor direction movement method, force joysticks respond to pressure, moveable ones respond to movement.
• Variable in degree of movement allowed, from horizontal-vertical only to continuous.

Advantages

i. Direct relationship between hand and pointer movement in terms of direction.

ii. Does not obscure vision of screen.

iii. Does not require additional desk space (if mounted on keyboard).

Disadvantages

i. Movement is indirect, in a plane different from the screen.

ii. Indirect relationship between hand and pointer movement in terms of speed and distance.

iii. Requires a degree of eye-hand coordination.

iv. Requires different hand movements.

v. May be slow and inaccurate.

vi. May be fatiguing to use over extended time.

3. Graphic Tablet

• Pressure-, heat-, light, or light-blockage-sensitive horizontal surfaces that lie the desktop or keyboard.
• May be operated with fingers, light pen, or objects like a stylus or pencil.
• Pointer imitates movements on tablet.

Advantages

i. Direct relationship between hand and pointer movement in terms of direction, distance and speed.

ii. Does not obscure vision of screen.

iii. More comfortable horizontal operating plane.

Disadvantages

i. Movement is indirect, in a plane different from the screen.

ii. Requires a degree of eye-hand coordination.

iii. Requires hand to be removed from keyboard and keyboard keys.

iv. Requires different hand movements.

v. Requires additional desk space.

vi. Finger may be too large for accuracy with small objects.

4. Touch Screen

A special surface on the screen sensitive to finger or stylus touches.

Advantages

i. Direct relationship between hand and pointer location in terms of direction, distance and speed.

ii. Requires no additional desk space.

iii. Movement is direct, in the same plane as screen.

iv. Stands up well in high-use environments.

Disadvantages

i. Finger may obscure part of screen.

ii. Finger may be too large for accuracy with small objects.

iii. Requires moving the hand far from the keyboard to use.

iv. Very fatiguing to use over extended period of time.

v. May soil or damage the screen.

5. Light Pen

It is a special surface on a screen sensitive to the touch of a special stylus or pen.

Advantages

i. Direct relationship between hand and pointer location in terms of direction, distance and speed.

ii. Requires minimal additional desk space.

iii. Movement is direct, in the same plane as screen.

iv. Stands up well in high-use environments.

v. More accurate than finger touching.

Disadvantages

i. Hand may obscure part of screen.

ii. Requires picking it up to use.

iii. Requires moving the hand far from the keyboard to use.

iv. Very fatiguing to use over extended period of time.

6. Voice

Automatic speech recognition by the computer.

Advantages

i. Simple and direct.

ii. Useful for people who cannot use a keyboard.

iii. Useful when the user’s hands are occupied.

Disadvantages

i. High error rates due to difficulties in recognizing boundaries between spoken words and blurred word boundaries due to normal speech patterns.

ii. Slower throughput than with typing.

iii. Difficult to use in noisy environments.

iv. Impractical to use in quiet environments.

7. Mouse

• A rectangular or dome-shaped, movable, desktop control containing from one to three buttons used to manipulate objects and information on the screen.
• Movement of screen pointer mimics the mouse movement.

Advantages

i. Direct relationship between hand and pointer movement in terms of direction, distance and speed.

ii. Does not obscure vision of screen.

iii. Permits a comfortable hand resting position.

iv. Selection mechanisms are included on mouse.

Disadvantages

i. Movement is indirect, in a plane different from the screen.

ii. Requires a degree of eye-hand coordination.

iii. Requires hand to be removed from keyboard.

iv. May require long movement distances.

v. Requires additional desk space.

8. Keyboard

It’s a standard typewriter keyboard and cursor movement keys.

Advantages

i. Familiar and accurate.

ii. Does not take up additional desk space.

iii. Very useful for:

• Entering text and alphanumeric data.
• Inserting in text and alphanumeric data.
• Keyed shortcuts – accelerators.
• Keyboard mnemonics – equivalents.

Disadvantages

i. Slow for non-touch-typists.

ii. Slower than other devices in pointing.

iii. Requires discrete actions to operate.

No direct relationship between finger or hand movement on the keys and cursor movement on screen in terms of speed and distance.