Upgrading and Repairing PCs

Wireless Input Devices

For several years, many manufacturers have offered cordless versions of mice and keyboards. In most cases, these devices have used either infrared or short-range radio transceivers to attach to standard serial or PS/2 ports, with matching transceivers located in the mouse or keyboard. Wireless input devices are designed to be easier to use in cramped home-office environments and where a large-screen TV/monitor device is used for home entertainment and computing.

Many manufacturers, including Microsoft, Logitech, and second-tier vendors, offer bundled kits that include a wireless keyboard and mouse which share a transceiver. Because many of these keyboards and mice have the latest features, including programmable keys, multimedia and Internet-access keys, and optical sensors, these wireless combos are often the top-of-the-line products from a given vendor and are often less expensive than buying the keyboard and mouse separately.

How Wireless Input Devices Work

The three major technologies used by wireless input devices are as follows:

• Infrared (IR)

• Proprietary radio frequency

• Bluetooth

All three technologies use a transceiver connected to the PS/2 or USB ports on the computer. Because many wireless transceivers are designed for use with a mouse and keyboard, PS/2-compatible versions have two cables—one for the mouse port and one for the keyboard port. A USB-compatible transceiver needs only one USB port to handle both devices if the system supports USB Legacy (keyboard) functions. The transceiver attached to the computer draws its power from the port.

The transceiver receives signals from the transceiver built in to the mouse or keyboard. These devices require batteries to function; therefore, a common cause of wireless device failure is battery run-down. Early generations of wireless devices used unusual battery types, but most recent products use off-the-shelf alkaline AA or AAA batteries. Rechargeable batteries are usually not supported, although Logitech's MX 700 has built-in rechargeable batteries and a transceiver that doubles as a charger.

Although all three technologies rely on battery power, the similarities end there. IR devices have a relatively short range (12 ft. maximum) and must have a clear line-of-sight between the input device and transceiver. Anything from a Mountain Dew can to a sheet of paper can block the IR signal from reaching the transceiver, assuming you're aiming the transmitter built in to your input device correctly in the first place. Some late-model IR devices have transceivers that can receive signals through a relatively wide 120° range, but this technology is much more temperamental than the others and has been abandoned by most vendors. Figure 18.15 shows how range and line-of-sight issues can prevent IR input devices from working correctly.

Because of the problems with IR devices shown in Figure 18.15, almost all vendors of wireless input devices now use radio waves (RF) for transmission between the device and transceiver. RF-based wireless devices have no line-of-sight problems, but most have a limited range of about 6 ft. from the transmitter (see Figure 18.16).

Although RF overcomes line-of-sight issues that can cripple an IR mouse, early versions of RF products had a high potential for interference from other devices and from other devices in use in the same room because of a limited range of channels. For example, early Logitech wireless MouseMan products required the user to manually select the channel used by the transceiver and mouse. If more than six users in a small room had wireless devices, interference was practically inevitable and user error could lead to a user's mouse movements showing up on the wrong computer screen.

Fortunately, improvements in frequency bands used and automatic tuning have enabled all users of a particular type of device to avoid interference with other electronic devices or with each other. For example, Logitech's current line of wireless products uses its patented Palomar technology. Although the 27MHz frequency used by Palomar has become a de facto standard for most recent wireless input devices (it's also used by Microsoft and IBM for their wireless products), Logitech allows users to enable a digital security feature that uses one of more than 4,000 unique codes to prevent accidentally activating another computer with a wireless device or signal snooping by another user. Most vendors use similar technology but might use a much smaller number of codes. The range of 27MHz RF devices is short—about 6 ft.—but the transmitter can be located behind the computer or under the desk without loss of signal.

Although most wireless products use proprietary radio transceivers, the Bluetooth wireless standard can now be used by some keyboards and mice, such as Microsoft's pioneering Wireless Optical Desktop mouse and keyboard bundle or the Wireless IntelliMouse Explorer for Bluetooth. Logitech also offers a Bluetooth-enabled input device: its Cordless Presenter handheld pointing device.

Bluetooth-enabled devices have an effective range of up to 30 ft. and might be compatible with other brands of devices that are also Bluetooth enabled.

Having used both IR and RF types of wireless devices, I can tell you that a radio-frequency input device beats an infrared input device hands down for use at home or in a small one- or two-person office. Because infrared requires an unobstructed direct line between the transceivers, when I used an infrared keyboard/pointing stick combination at a client site, I was constantly re-aiming the keyboard at the transceiver to avoid losing my signal. When I used a radio mouse, on the other hand, there were no line-of-sight issues to worry about. Historically, the only advantage to infrared was cost, but the problems of reliability in my mind outweigh any cost savings. Additionally, a wide range of prices for RF wireless products, including attractive keyboard and mouse combinations, make RF input devices affordable for almost everyone. If you're planning to use a computer to drive a big-screen TV or as a presentation unit, consider Bluetooth-enabled devices available from Microsoft, Logitech, and others because of their longer range (up to 10 meters, or 33 ft.).

Power Management Features of Wireless Input Devices

A wireless mouse is useless if its batteries fail, so several vendors of wireless products have developed sophisticated power-management features to help preserve battery life—especially with optical mice, which use power-eating LEDs to illuminate the mousing surface. For example, the Logitech Cordless MouseMan Optical's LED sensor has four operating modes, as shown in Table 18.6.

Table 18.6. Logitech Cordless MouseMan Optical Power Management

Mode	LED Flashing Rate	Notes
Normal	1,500 per second	Used only when mouse is being moved across a surface
Glow	1,000 per second	Used when mouse stops moving
Strobe	10 per second	Mouse not moved for more than 2 minutes
Flash	2 per second	Mouse not moved for more than 10 minutes

Wireless keyboards are activated only when you press a key or use the scroll wheel available on some models, so they tend to have longer battery lives than mice. Conventional ball-type mice also have longer battery lives than optical mice, but the convenience and accuracy of optical mice outweigh battery-life issues for most users.

Wireless Pointing Device Issues

Before you invest in wireless pointing devices for multiple computers, you should be aware of the following issues:

• Line-of-site issues. Infrared devices won't work if the IR beam between the pointing device and the transceiver attached to the system is blocked. These units are not as suitable for casual in-the-lap use as radio-frequency units are.

• Radio-frequency interference. Although early wireless mice used analog tuners that were hard to synchronize, today's wireless input devices typically use digital selectors. However, if several similar devices are used in close quarters, a transceiver might actually receive data from the wrong mouse or keyboard. Also, metal desks and furniture can reduce range and cause erratic cursor movement. Most wireless devices operate around 27MHz, minimizing interference from devices such as cordless phones. If you plan to install several different computers using wireless input devices in the same room, set up one at a time and allow about half an hour between installations if possible to let each unit synchronize with its transceiver. Check with the vendor for other tips on overcoming interference issues.

• Battery life and availability. Early wireless devices sometimes used unusual, expensive batteries. Today's units run on common battery types, such as AAA or AA. Battery life is usually rated at about 6 months for keyboards or ball-type mice and about 2–3 months for optical mice. Be sure you have spare batteries for the input device to avoid failures due to running out of battery power. Some vendors provide software that gives users an onscreen warning when batteries run low. Furthermore, when using an optical wireless mouse, you should try working on brighter or whiter surfaces. Many optical mice adjust their sensors based on the illumination of the surface, which is why you might see the light in the mouse change intensity. The less intense the internal LED operates, the less battery power being used.

• Location. The range of wireless devices can vary from 6 ft. with conventional RF devices to as much as 30 ft. with Bluetooth-based devices. Consider where the device will be used before making your purchase. For instance, in an office where multiple devices might be used at the same time, a close-range device might be more desirable to avoid cross talk among devices. On the other hand, the home user who wants to sit away from the screen while maintaining control might want an extended range, making Bluetooth-enabled devices a better choice.

• User experience. Different users will have different expectations of wireless input devices, but in general, the more a wireless input device acts like its wired siblings, the better. The fact that a device is wireless should not compromise its functionality. If things such as reliability, connection, or driver problems hinder proper usage, the device isn't worth using. Hardcore gamers who need the fastest response time possible generally favor the responsiveness of a wired optical mouse over any wireless mouse. Although minimal, some lag time does exist. Some mice can require up to 0.25 centimeter of movement before responding. This lag time can also affect users doing graphical work requiring the superior consistency and accuracy of a wired optical mouse, although the latest dual-sensor wireless optical mice have accuracy on par with wired optical mice.

• Pointer speed. Conventional wired optical mice transmit their positions about 120 times per second, whereas wireless mice that use a USB receiver transmit their positions about 40–50 times per second. If you use a mouse to play fast-action games, you might find a corded mouse a better choice because of the more frequent position updates it provides.

Troubleshooting Wireless Input Devices

If your wireless input device does not work, check the following:

• Battery failure. The transceivers attached to the computer are powered by the computer, but the input devices themselves are battery-powered. Check the battery life suggestions published by the vendor; if your unit isn't running as long as it should, try using a better brand of battery or turning off the device if possible.

• Lost synchronization between device and transceiver. Both the device and the transceiver must be using the same frequency to communicate. Depending on the device, you might be able to resynchronize the device and transceiver by pressing a button, or you might need to remove the battery, reinsert the battery, and wait for several minutes to reestablish contact.

• Interference between units. Check the transmission range of the transceivers in your wireless units and visit the manufacturer's Web site for details on how to reduce interference. Typically, you should use different frequencies for wireless devices on adjacent computers.

• Blocked line of sight. If you are using infrared wireless devices, check the line of sight carefully at the computer, the space between your device and the computer, and the device itself. You might be dangling a finger or two over the infrared eye and cutting off the signal—the equivalent of putting your finger over the lens on a camera.

• Serial port IRQ conflicts. If the wireless mouse is connected to a serial port and it stops working after you install another add-on card, check for conflicts using the Windows Device Manager.

• Disconnected transceiver. If you have moved the computer around, you might have disconnected the transceiver from its keyboard, PS/2 mouse, serial, or USB port. You can plug a USB device in without shutting down the system, but the other types require you to shut down, reattach the cable, and restart to work correctly.

• USB Legacy support not enabled. If your wireless keyboard uses a transceiver connected to the USB port and the device works in Windows, but not at a command prompt, make sure you have enabled USB Legacy support in the BIOS or use the PS/2 connector from the transceiver to connect to the PS/2 keyboard port.