Datasheet

Input and Peripheral Devices 57
Be able to determine the cause of display system problems. The most common display
problems relate to power, brightness, or contrast. Adjusting the monitor controls should be
your first step when troubleshooting.
Input and Peripheral Devices
A virtually unlimited number of types of input devices can be connected to a PC. In addition
to the standard keyboard and mouse, there are bar-code readers, digital cameras, micro-
phones, biometric devices, touch screens, and a plethora of others. Many today connect
through the USB or FireWire port, using instructions from the vendor. However, you must
know about other types of connections for the A+ exam.
Critical Information
Keyboard connectors allow for the direct connection of the keyboard to the motherboard.
There are essentially three types of keyboard connectors: AT, PS/2, and USB.
AT connectors are round, about 1
1
⁄2˝ in diameter, and have five sockets in the DIN-5 con-
figuration. They’re found on AT motherboards. The second style, PS/2 connectors, are smaller
and look just like a PS/2 mouse connector; these are found on ATX motherboards. USB key-
boards are rapidly growing in popularity and allow you to connect to any available USB port
(front, back, side, etc.).
A mouse connector is a PS/2-style connector; on an ATX it’s built into the side of the
motherboard, and on an AT a small ribbon cable connects a back-mountable port to
the motherboard.
Troubleshooting Keyboard and Mouse Problems
Usually, keyboard problems are environmental. Keyboards get dirty, and the keys start
to stick.
If a keyboard is malfunctioning (for example, sending the wrong characters
to the display), it’s most cost-effective to replace it rather than spend hours
attempting to fix it, because keyboards are fairly inexpensive.
One way to clean a keyboard is with the keyboard cleaner sold by electronics supply
stores. This cleaner foams up quickly and doesn’t leave a residue behind. Spray it liberally
on the keyboard and keys. Work the cleaner in between the keys with a stiff toothbrush.
Blow away the excess with a strong blast of compressed air. Repeat until the keyboard
functions properly. If you have to clean a keyboard that’s had a soft drink spilled on it,
remove the key caps before you perform the cleaning procedure; doing so makes it easier
to reach the sticky plungers.
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