T11 - Keyboard & Mouse

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    Keyboard

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    Mouse

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    Keyboard

    One of the most basic system components is the

    keyboard, which is the primary input device. It is used for

    entering commands and data into the system.

    The primary keyboard types are as follows: 101-key Enhanced keyboard

    104-key Windows keyboard

    83-key PC and XT keyboard (obsolete)

    84-key AT keyboard (obsolete)

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    Keyswitch Design

    Todays keyboards use any one of several switch types

    to create the action for each key. Most keyboards use a

    variation of the mechanical keyswitch. A mechanical

    keyswitch relies on a mechanical momentary contact-

    type switch to make the electrical contact that forms acircuit. Some high-end keyboards use a more

    sophisticated design that relies on capacitive switches.

    The most common type of keyswitch is the mechanical

    type, available in the following variations: Pure mechanical

    Foam element

    Rubber dome

    Membrane (most common)3

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    Membrane Keyswitch

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    Keyboard Interface

    A keyboard consists of a set of switches mounted in a gridor an array called the key matrix. When a switch is

    pressed, a processor in the keyboard identifies which key

    is pressed. The keyboard processor can even handle

    multiple keypresses at the same time. A 16-byte hardwarebuffer in the keyboard can handle rapid or multiple

    keypresses, passing each one to the system in

    succession.

    The keyboard send signal to the PC via onr of the

    following interface:

    AT Serial (DIN 5) (No longer use)

    PS/2

    USB

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    Keyboard Connector

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    Keyboard Troubleshooting

    Keyboard errors are usually caused by two simpleproblems. Other more difficult, intermittent problems can

    arise, but they are much less common. The most frequent

    problems are as follows:

    Defective cables Stuck keys

    Defective cables are easy to spot if the failure is not

    intermittent. If the keyboard stops working altogether or

    every keystroke results in an error or incorrect character,

    the cable is likely the culprit. Troubleshooting is simple,

    replace the keyboard with a known working keyboard to

    verify whether the problem still exists. If it does, the

    problem must be elsewhere.

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    Keyboard Maintenance

    One of the best ways to keep a keyboard in top conditionis periodic cleaning. As preventive maintenance, you

    should vacuum the keyboard monthly. You also can use

    canned compressed air to blow the dust and dirt out

    instead of using a vacuum. Before you dust a keyboardwith the compressed air, turn the keyboard upside down

    so that the dirt and dust collected inside can fall out.

    On all keyboards, each keycap is removable, which can

    be handy if a key sticks. For example, a common problem

    is a key that does not work every time you press it. This

    problem usually results from dirt collecting under the key.

    Remove the cap, spray some compressed air into the

    space under the cap to dislodge the dirt. Then replace the

    cap and check the action of the key. 8

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    Keyboard Maintenance

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    Mouse

    A standard mouse consists of several components: A housing that you hold in your hand and move around on your

    desktop

    A method of transmitting movement to the system: either ball/roller

    or optical sensors

    Buttons (two or more, and often a wheel or toggle switch) for

    making selections

    An interface for connecting the mouse to the system; conventional

    mice use a wire and connector, whereas wireless mice use a

    radio-frequency or infrared transceiver in both the mouse and a

    separate unit connected to the computer to interface the mouse to

    the computer

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    Mouse

    Two types of commonly used mouse : Mechanical mouse

    the bottom of the housing contains a small, rubber ball that rolls as you move

    the mouse across the tabletop. The movements of this rubber ball are

    translated into electrical signals transmitted to the computer across the cable.

    Need to clean regularly

    Optical mouse (most common)

    using an optoelectronic sensor to take successive images of the surface on

    which the mouse operates. The mouse then detect relative motion on a wide

    variety of surfaces, translating the movement of the mouse into the movement

    of the cursor.

    Laser mouse Laser mouse works like optical mouse. The only different is that it uses laser

    light instead of LED. The use of laser enable this type of mouse to work in most

    of the surfaces including glass.

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    Mechanical Mouse

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    Operating a mechanical

    mouse.

    1. Moving the mouse turns the

    ball.

    2. X and Y rollers grip the balland transfer movement.

    3. Optical encoding disks include

    light holes.

    4. Infrared LEDs shine through

    the disks.

    5. Sensors gather light pulses to

    convert to X and Y velocities.

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    Optical Mouse

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    Mouse Interface

    The connector used to attach your mouse to the systemdepends on the type of interface you are using. Mice are

    most commonly connected to your computer through the

    following interfaces:

    Serial interface (obsolete) Dedicated motherboard (PS/2) mouse port

    USB port

    Bluetooth or other wireless connection

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    Wireless Keyboard/Mouse

    The three major technologies used by wireless inputdevices are as follows:

    Infrared (IR)

    Proprietary radio frequency (RF)

    Bluetooth All three technologies use a transceiver connected to the

    PS/2 or USB ports on the computer.

    The transceiver receives signals from the transceiver built

    in to the mouse or keyboard. These devices requirebatteries to function; therefore, a common cause of

    wireless device failure is battery run-down.

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    Wireless Keyboard/Mouse

    IR devices have a relatively short range (12 ft. maximum)and must have a clear line-of-sight between the input

    device and transceiver.

    Most wireless mouse/keyboard nowadays are using either

    RF or Bluetooth. Both technologies do not require line-of-sight but RF has very short range (6 ft.).

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    Other Input Devices

    Microphone (sound input) Webcam (video input)

    Touch screen

    Joystick / game pad

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