External Pointing Devices

Once you have decided on which interface to use, several different types of external pointing devices are available. This section describes the most popular choices.

Mice

Mice come in many shapes and sizes and from many manufacturers. Some have taken the standard mouse design and turned it upside down, creating the trackball .

The largest manufacturers of mice are Microsoft and Logitech; these two companies provide designs that inspire the rest of the industry (and each other) and are popular OEM choices as well as retail brands. Even though mice can come in different varieties, their actual use and care differ very little. The 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 (RF) or infrared (IR) transceiver in both the mouse and a separate unit connected to the computer to interface the mouse to the computer.

The housing, which is made of plastic, consists of very few moving parts . On top of the housing, where your fingers normally rest, are buttons. There might be any number of buttons, but in the PC world, two is the standard. If additional buttons or a wheel are on your mouse, specialized driver software provided by the mouse vendor is required for them to operate to their full potential. Although the latest versions of Windows support scrolling mice, other features supported by the vendor still require installing the vendor's own mouse driver software.

The bottom of the mouse housing is where the detection mechanisms or electronics are located. On traditional mice, 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.

Mechanical Mice

Internally, a ball-driven mouse is very simple, too. The ball usually rests against two rollers: one for translating the X-axis movement, and the other for translating the Y-axis movement. These rollers are usually connected to small disks with shutters that alternately block and allow the passage of light. Small optical sensors detect movement of the wheels by watching an internal infrared light blink on and off as the shutter wheel rotates and "chops" the light. These blinks are translated into movement along the axes. This type of setup, called an opto-mechanical mechanism , was the most popular mechanism prior to the advent of inexpensive optical technology (see Figure 13.18).

Figure 13.18. Typical opto-mechanical mouse mechanism.

Optical Mice

The other major method of motion detection is optical. Some of the early mice made by Mouse Systems and a few other vendors used a sensor that required a special grid- marked pad. Although these mice were very accurate, the need to use them with a pad caused them to fall out of favor.

Microsoft's IntelliMouse Explorer pioneered the return of optical mice, but with a difference. Like the old-style optical mice, the IntelliMouse Explorer uses optical technology to detect movement, and it has no moving parts itself (except for the scroll wheel and buttons on top). The Explorer mouse needs no pad; it can work on virtually any surface. This is done by upgrading the optical sensor from the simple type used in older optical mice to a more advanced charge coupled device (CCD). This essentially is a crude version of a video camera sensor that detects movement by seeing the surface move under the mouse. An LED is used to provide light for the sensor.

The IntelliMouse Explorer was just the first of a growing family of optical mice made by Microsoft (the IntelliMouse Optical and WheelMouse Optical are less expensive versions), and Microsoft also offers an optical-technology trackball. Logitech also offers optical mice (including one with two sensors) and optical trackballs using similar technology. Because of greater precision and reliability, optical technology has become the dominant technology in modern mice and trackballs (see Figure 13.19).

Figure 13.19. The bottom of the Logitech iFeel optical mouse.

Their versatility and low maintenance (not to mention that neat red glow out the sides!) make optical mice an attractive choice, and the variety of models available from both vendors means you can have the latest optical technology for about the price of a good ball-type mouse.

The cable can be any length, but it is typically between 4 and 6 feet long. Mice are also available in a cordless design, which uses either IR or RF transceivers to replace the cable. A receiver is plugged into the mouse port, whereas the battery- powered mouse contains a compatible transmitter.

Tip

If you have a choice on the length of cable to buy, go for a longer one. This allows easier placement of the mouse in relation to your computer. Extension cables can be used if necessary.

Mouse Drivers

After the mouse is connected to your computer, it communicates with your system through the use of a device driver, which can be loaded explicitly or built in to the operating system software. For example, no separate drivers are necessary to use a mouse with Windows or OS/2, but using the mouse with most DOS-based programs requires a separate driver to be loaded from the CONFIG.SYS or AUTOEXEC.BAT file. Regardless of whether it is built in, the driver translates the electrical signals sent from the mouse into positional information and indicates the status of the buttons.

The standard mouse drivers in Windows are designed for the traditional two-button mouse or scroll mouse (in Windows Me/2000/XP or later), but increasing numbers of mice feature additional buttons, toggles, or wheels to make the mouse more useful. These additional features require special mouse driver software supplied by the manufacturer.

Trackballs

The first trackball I ever saw outside of an arcade was the Wico trackball, a perfect match for mid-1980s video games and computer games , such as Missile Command and others. It emulated the eight-position Atari 2600 analog joystick, but was capable of much more flexibility.

Unlike the mid-80s trackballs, today's trackballs are used primarily for business instead of gaming. Most trackballs use a mouse-style positioning mechanism ”the differences being that the trackball is on the top or side of the case and is much larger than a mouse ball. The user moves the trackball rather than the input device case, but rollers or wheels inside most models translate the trackball's motion and move a cursor onscreen the same way that mouse rollers or wheels convert the mouse ball's motion into cursor movement.

Trackballs come in a variety of forms, including ergonomic models shaped to fit the (right) hand, ambidextrous models suitable for both left- and right-handers, optical models that use the same optical sensors found in the latest mice in place of wheels and rollers, and multibutton monsters that look as if they're the product of a meeting with a remote control.

Because they are larger than mice, trackballs lend themselves well to the extra electronics and battery power needed for wireless use. Logitech offers several wireless trackball models that use radio-frequency transceivers; for details of how this technology works, see the following section, "Wireless Input Devices."

Trackballs use the same drivers and connectors as conventional mice. For basic operations, the operating system “supplied drivers will work, but you should use the latest version of the vendor-supplied drivers to achieve maximum performance with recent models.