Basic Hardware

Cables and Wires

• Although these are not the most sophisticated part of the system, they are just as important as any other component.
• All the components in a PC are connected together and to power with wires and cables.
  
• Ninety percent of all electronics problems (including PCs) are the result of poor connections.
• If you have a PC problem, it is always a good idea to first check that all the cables on your PC are plugged in and properly seated.

Audio

• Speakers and headphones are the primary audio output devices for a PC.

• Some monitors have speakers built into their sides. Other speakers are free standing.
  
• Passive speakers plug into and are powered directly from the output signal provided by the ‘speaker out’ port on the sound card.
• Active speakers amplify the sound signal from the sound card using battery or rectified AC house power.

Mouse

The mouse is the most common ‘pointing device’ used in PCs. Every mouse has two buttons and most have one or two scroll wheels.

• By default the left button is used to select items. The right button is assigned as a context or alternate menu. A single wheel is normally set to scroll up and down on the active page . If a second wheel is present, it is usually assigned to scroll left and right on the page.

• The button functions can be reassigned by going to Control Panel > Mouse > Buttons tab.

• Data is transferred to the PC over a short cable with a circular 6-pin Mini-din connector that plugs into the back of the motherboard. This type of mouse sells for $10 to $25 depending on the style, button and wheel configuration.

• Some versions of the mouse are wireless. They communicate with a receiver pod that is plugs into the mouse port. Radio Frequency (RF) or InfraRed (IR) technology is used for communication between the mouse and the pod. These sell in the $30 to $45 range.

There are two designs used in a mouse for detecting motion:

Track ball:
This type of mouse uses a rolling (track) ball. As the mouse moves the ball rolls. The rolling motion is converted electronically into matching movements of the mouse pointer that moves across your video display.
The track ball mouse is rapidly becoming another casualty of rapidly changing technology. The optical mouse has pretty much replaced it. The track ball mouse is already becoming a thing of the past.

Optical:
This mouse uses an InfraRed transmitter/receiver pair to optically detect the motion of the mouse. It has a number of advantages over the track ball mouse:

• No mouse pad is required.
• Can work on any flat surface
• No rolling track ball that collects and transfers dirt to the internal rollers, making them slip. When they do, your mouse pointer jumps around in an unpredictable and annoying way!

See the Easy Tips section of this web site for an explanation on how to clean a track ball mouse.

Keyboard

• The keyboard was the first input device developed for the PC.
• The standard keyboard layout provides 104 keys organized as four groups:
  • alphanumeric keys (A-Z, 0-9)
  • location keys (home, end etc.)
  • numeric keypad
  • function keys (F1-F12)

In addition to the standard keys, some keyboards offer functions such as volume control for speakers, web browser functions and power management.

• Data is transferred to the PC over a short cable with a circular 6-pin Mini-din connector that plugs into the back of the motherboard.
• Standard keyboards sell for $7 to $30 depending on the feature set.
• There are wireless keyboards that communicate with a pod that is plugged into the keyboard port. Radio Frequency (RF) or InfraRed (IR) technology is used to communicate between the keyboard and the receiver pod, which plugs into the PC. Wireless keyboards are priced in the $40 to $45 range.
• Cherry Hill Inc. is releasing a keyboard that has an integrated Finger Tip sensor. Instead of having to type in passwords to access the PC a successful fingerprint match allows entry in to the PC or specific programs.

Compact Disk Drive

• The CDD installs in one of the external 5-1/4 inch drive bays in the front of the PC case. It is secured by machine screws. Some manufacturers offer special rail-like systems that mount on the CDD. These allow the drive to be removed from the PC without having to remove any screws.
• Data is stored optically on the surface of the disk. A laser attached to an arm that moves back and forth across near the disk surface and sends light toward the disk surface which is coated with of a thin layer of aluminum.
  
• Smooth areas called a lands reflect the light back to a photo diode located near the laser. The reflected light is read as a 1. Areas called pits are where the aluminum has been removed. When the laser light hits these, it is scattered and very little is picked up by the photo diode. The absence of light is read as a 0.
• CDD have become the predominant removable storage media for PCs and can store 700 Mbytes of data.
• A 4-pin cable from the power supply plugs into the CDD and provides power to it.
• Data to and from the motherboard is carried on a 40-pin IDE (Integrated Drive Electronics) cable.
• There are two types of Compact Disk drives available for PCs.
1. CD-ROM (read only memory) is the older type. As the title implies it can only read CDs. It can read any standard CD and most CD-R type disks. It may be able to read some types of CD-RW disks too.
2. CD-RW (ReWritable)units can read and write CD-R and CD-RW type disks. It can also read standard CD type disks.
   A 24x10x40 CD-RW unit. The 24x10x40 means the unit can write at 24x, re-write at 10x and read at 40x, where x is 150Kbytes/sec.

Hard Disk Drive

• The HDD installs in one of the 3-1/2 inch internal drive bays in the PC. It is secured by machine screws.
• It is powered by a 4 conductor cable coming from the power supply.
• Data to and from the motherboard is carried on a 40-pin IDE (Integrated Drive Electronics) cable.
• Data is stored magnetically on multiple rigid disks that are stacked up like pancakes. Small arms with magnetic pickups move rapidly back and forth across the top and bottom surface of each disk in the drive. The sensors float just a few microns above the rotating disk surface and can read and write data at very high rates.
• Most commercially available hard drives rotate at 5400 or 7200 RPM (revolutions per minute) which translates to 90 or 120 revolutions per second respectively. The data transfer rate from the drive to the motherboard is 33 Mbytes/second in bursts. Newer drives are capable of higher speeds up to 66 Mbytes/sec. To use this faster drive, the PC must have an ATA/66 interface that is capable of keeping up with it.

Power Supply

• A power supply is installed in the back corner of the PC case, next to the motherboard.
• It converts 120vac (standard house power) into DC voltages that are used by other components in the PC.
• A 20 conductor cable carries +5vdc, -5vdc +12vdc, -12vdc and ground to the motherboard.
• Another pair of cables, each with four conductors and two 4-pin connectors daisy-chained along it, carry +5vdc, +12vdc and ground to the drives (hard, floppy and CD/DVD).
• Typical PC power supplies are rated at 200-250 watts and higher wattage supplies are available.