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.