Hardware Reference
In-Depth Information
• Proprietary radio frequency
• Bluetooth
All three technologies normally use a transceiver connected to the USB or PS/2 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 into the mouse or keyboard. These devices
require batteries to function; therefore, a common cause of wireless device failure is battery
rundown. Early generations of wireless devices used unusual battery types, but most recent products
use off-the-shelf AA or AAA batteries, including rechargeables. Some have internal lithium-ion or
NiMH rechargeable batteries, in which the transceiver connected to the PC also doubles as a charger.
Some are rechargeable via special docks or USB cable connections.
Although all three technologies rely on battery power, the similarities end there. IR devices have a
relatively short range (12 ft. maximum), and a clear line-of-sight must exist 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 into 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.
Because of the problems with IR devices, almost all vendors of wireless input devices now use radio
frequency (RF) signals for transmission between the device and transceiver. RF-based wireless
devices have no line-of-sight problems, but they can vary in the maximum distances they will allow
from the transmitter.
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, some early wireless 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.
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, the 27MHz frequency pioneered by Logitech's Palomar line of peripherals has become a de
facto standard for most recent wireless input devices. (Microsoft and IBM have also used it 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 some might use a much
smaller number of codes. Many recent wireless products use FastRF technology, which provides 2.5
times the transmission rate of conventional 27MHz devices. The responsiveness of a FastRF
connection is all but indistinguishable from a corded mouse or keyboard.
Finally, there's Bluetooth. Although most wireless products use proprietary radio transceivers,
Microsoft, Logitech, and some others have developed wireless mouse and keyboard products using
the Bluetooth wireless standard. Bluetooth-enabled devices have an effective range of up to 30 feet
