5 keyboard mouse_scanner


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  • Recall that COM 1 and COM 3 share IRQ 4 while COM 2 and COM 4 share IRQ 3- if the Mouse is using a COM port, the port on the same channel cannot be used
  • As we all know too well, today’s telephone lines are limited to 56Kbps transmission speed at best Know the signal abbreviations for certification
  • 5 keyboard mouse_scanner

    1. 1. Peripheral Devices
    2. 2. Keyboards <ul><li>Keyswitch Keyboards- employ an individual switch under each key- a plunger moves downward in response to a key press, making a connection between two signal lines coming from the keyboard controller </li></ul><ul><ul><li>Inexpensive </li></ul></ul><ul><ul><li>Simple to make </li></ul></ul><ul><ul><li>Simple to service </li></ul></ul><ul><ul><li>Bounce led to duplicate letters, but decreased tension leads to finger fatigue </li></ul></ul><ul><ul><li>Bulky </li></ul></ul><ul><ul><li>Require Voltage to operate </li></ul></ul><ul><li>Second effort employed an electric controller to constantly scan for keystrokes, ignoring those which are not present for a second scan </li></ul>
    3. 3. Capacitive Keyboards <ul><li>Placed two sheets of semi-conductive materials separated by a thin sheet of Mylar inside the keyboard- a key press creates contact between the sheets changing the capacitance- the controller is aware of which key is pressed by reading a scan code </li></ul><ul><ul><li>You cannot repair capacitive switch keyboards </li></ul></ul><ul><ul><li>Durable </li></ul></ul><ul><ul><li>Inexpensive </li></ul></ul>
    4. 4. Keyboard Connectors <ul><li>DIN 5- standard on the IBM PC or XT/AT form factor machines </li></ul><ul><li>Mini- PS/2- smaller then the DIN 5- so named because it was initially introduced on the IBM PS/2 </li></ul>
    5. 5. Cleaning Keyboards <ul><li>Remove it from the computer and soak it in distilled, demineralized water as soon as a spill occurs </li></ul><ul><ul><li>A dry spill is much harder to clean </li></ul></ul><ul><ul><li>Running keyboard through the dishwasher is not recommended </li></ul></ul><ul><ul><li>Be sure the keyboard is completely dry before reconnecting it and using it </li></ul></ul><ul><li>Disassemble and use a special keyboard cleaner </li></ul><ul><ul><li>Due to the amount of time this method requires, it is cheaper to simply buy a new keyboard </li></ul></ul>
    6. 6. The Mouse <ul><li>GUI - Graphical User Interface- the use of pictures to represent computer entities or basic commands (i.e.- save, exit) </li></ul><ul><li>Mouse - a device specifically designed to interact with the pictures represented in a GUI interface- translates moves on a horizontal surface into movements of a pointer on the screen </li></ul>
    7. 7. Types of Mice <ul><li>Opto-mechanical- contains a round ball that makes contact with two internal rollers representing the x and y axis respectively- optical sensors interpret light patterns as speed and direction of movement and send those to the mouse control software on the computer </li></ul><ul><li>An Optical Mouse has no ball- rather it uses a special mouse pad and a beam of laser light- the pad reflects the laser back to a sensor in the mouse that detects movement and direction </li></ul><ul><ul><li>Will not work without the special mouse pad </li></ul></ul>
    8. 8. Mouse Interfaces <ul><li>Serial – the first major mouse interface was a DB9 serial </li></ul><ul><ul><li>Major disadvantage was the use of a COM port </li></ul></ul><ul><li>Bus Interface- an expansion card with a PS/2 connector </li></ul><ul><ul><li>Did not take up a COM port, but it does use an interrupt </li></ul></ul><ul><li>PS/2 Mouse Interface - the same PS/2 connector integrated on the motherboard </li></ul>
    9. 9. Cleaning the Mouse <ul><li>1. Turn the mouse upside down and remove the ball by rotating the retaining ring </li></ul><ul><li>2. Flip the mouse upright so the ball will fall out </li></ul><ul><li>3. Use a small eyeglass screwdriver to remove the circular accumulation of dust and dirt on the rollers </li></ul><ul><li>4. If needed, soak in isopropyl alcohol to loosen </li></ul><ul><li>5. Reassemble </li></ul>
    10. 10. Other Pointing Devices <ul><li>Trackballs - essentially an upside-down mouse- the ball moves while the casing is stationary- typical trackballs are large desktop style- portable trackballs are more compact and may be held in the hand </li></ul><ul><li>Drawing Tablets - a sheet of plastic with a rubberized coating on which a user my use a stylus to “draw” images </li></ul><ul><ul><li>Electromagnetic Tablets- tablet has a grid of wires across which an electrical pulse is sent at regular intervals- a sensor in the stylus translates the signals to x and y coordinates </li></ul></ul><ul><ul><li>Resistive Tablets - have a resistive surface under the rubberized coating that induces variable current at different spots on the x and y axis translating to specific coordinates </li></ul></ul><ul><ul><li>Acoustic Tablets - stylus has a small spark which activates at the press of a button- microphones on the x and y axis translate the coordinates into values for the computer </li></ul></ul><ul><li>Touch Screens- a screen which is sensitive to touch </li></ul><ul><ul><li>Optical - the physical touch breaks a beam of light emanating from the screen to determine x and y coordinates </li></ul></ul><ul><ul><li>Capacitive screens- like the keyboards, employ two sheets of clear plastic separated by a layer of air- touching a particular spot changes the total capacitance and translates to an x, y coordinate </li></ul></ul>
    11. 11. Scanners <ul><li>Flatbed Scanners - resemble the top half of a photocopier- they employ a charge coupled device, a motorized carriage, and a light source to convert images in to computerized files </li></ul><ul><ul><li>Usually SCSI </li></ul></ul><ul><ul><li>Can be manufacturer proprietary </li></ul></ul><ul><li>Handheld Scanners - contain all the same components in a smaller enclosure with wheels </li></ul><ul><ul><li>Inexpensive </li></ul></ul><ul><ul><li>Decent Capabilities </li></ul></ul><ul><ul><li>Slow </li></ul></ul><ul><ul><li>Quality Depends Largely on User </li></ul></ul><ul><ul><li>Scanners may be cleaned carefully with glass cleaner </li></ul></ul>
    12. 12. Modems <ul><li>Modem actually stands for Modulator/Demodulator- digital signals can lose strength over long distances- analog signals may get weaker, but the sound does not degrade- therefore, analog signals are a better choice for communication over a telephone line. The modem translates the digital signals from the computer to analog signals for transmission and visa versa </li></ul><ul><ul><li>Modem Signal Abbreviations </li></ul></ul><ul><ul><li>OH- Off the Hook </li></ul></ul><ul><ul><li>SD(TX) Transmit Data </li></ul></ul><ul><ul><li>RD(RX) Receive Data </li></ul></ul><ul><ul><li>AA Auto Answer </li></ul></ul>