Wireless Mice

Most wireless mice use radio frequency (RF) technology to
communicate information to your computer. Being radio-based,
RF devices require two main components: a transmitter and
a receiver. Here's how it works:

* The transmitter is housed in the mouse. It sends
an electromagnetic (radio) signal that encodes the
information about the mouse's movements and the buttons you
click.
* The receiver, which is connected to your computer,
accepts the signal, decodes it and passes it on to the mouse
driver software and your computer's operating system.
* The receiver can be a separate device that plugs into
your computer, a special card that you place in an expansion
slot, or a built-in component.

Many electronic devices use radio frequencies to communicate.
Examples include cellular phones, wireless networks, and
garage door openers. To communicate without conflicts,
different types of devices have been assigned different
frequencies. Newer cell phones use a frequency of 900
megahertz, garage door openers operate at a frequency of 40
megahertz, and 802.11b/g wireless networks operate at 2.4
gigahertz. Megahertz (MHz) means "one million cycles per
second," so "900 megahertz" means that there are 900 million
electromagnetic waves per second. Gigahertz (GHz) means "one
billion cycles per second." To learn more about RF and
frequencies, see How the Radio Spectrum Works.

Unlike infrared technology, which is commonly used for
short-range wireless communications such as television remote
controls, RF devices do not need a clear line of sight
between the transmitter (mouse) and receiver. Just like other
types of devices that use radio waves to communicate,
a wireless mouse signal can pass through barriers such as
a desk or your monitor.

RF technology provides a number of additional benefits for
wireless mice. These include:

* RF transmitters require low power and can run on
batteries
* RF components are inexpensive
* RF components are light weight

As with most mice on the market today, wireless mice use
optical sensor technology rather than the earlier track-ball
system. Optical technology improves accuracy and lets you use
the wireless mouse on almost any surface -- an important
feature when you're not tied to your computer by a cord.

Pairing and Security
In order for the transmitter in the mouse to communicate with
its receiver, they must be paired. This means that both
devices are operating at the same frequency on the same
channel using a common identification code. A channel is
simply a specific frequency and code. The purpose of pairing
is to filter out interference from other sources and RF
devices.

Pairing methods vary, depending on the mouse manufacturer.
Some devices come pre-paired. Others use methods such as
a pairing sequence that occurs automatically, when you push
specific buttons, or when you turn a dial on the receiver
and/or mouse.

To protect the information your mouse transmits to the
receiver, most wireless mice include an encryption scheme to
encode data into an unreadable format. Some devices also use
a frequency hopping method, which causes the mouse and
receiver to automatically change frequencies using
a predetermined pattern. This provides additional protection
from interference and eavesdropping.

Bluetooth Mice

One of the RF technologies that wireless mice commonly use is
Bluetooth. Bluetooth technology wirelessly connects
peripherals such as printers, headsets, keyboards and mice to
Bluetooth-enabled devices such as computers and personal
digital assistants (PDAs). Because a Bluetooth receiver can
accommodate multiple Bluetooth peripherals at one time,
Bluetooth is also known as a personal area network (PAN).
Bluetooth devices have a range of about 33 feet (10 meters).

Bluetooth operates in the 2.4 GHz range using RF technology.
It avoids interference among multiple Bluetooth peripherals
through a technique called spread-spectrum frequency hopping.
WiFi devices such as 802.11b/g wireless networks also operate
in the 2.4 GHz range, as do some cordless telephonescordless
telephones and microwave ovens. Version 1.2 of Bluetooth
provides adaptive frequency hopping (AFH), which is
an enhanced frequency-hopping technology designed to avoid
interference with other 2.4 GHz communications.

RF Mice

The other common type of wireless mouse is an RF device that
operates at 27 MHz and has a range of about 6 feet (2
meters). More recently, 2.4 GHz RF mice have hit the market
with the advantage of a longer range -- about 33 feet (10
meters) and faster transmissions with less interference.
Multiple RF mice in one room can result in cross-talk, which
means that the receiver inadvertently picks up the
transmissions from the wrong mouse. Pairing and multiple
channels help to avoid this problem.

Typically, the RF receiver plugs into a USB port and does not
accept any peripherals other than the mouse (and perhaps
a keyboard, if sold with the mouse). Some portable models
designed for use with notebook computers come with a compact
receiver that can be stored in a slot inside the mouse when
not in use.

Mouse Innovations

As with many computer-related devices, mice are being
combined with other gadgets and technologies to create
improved and multipurpose devices. Examples include
multi-media mice, combination mice/remote controls, gaming
mice, biometric mice, tilting wheel mice and motion-based
mice. To learn more about innovations in mouse technology,
let's start with multi-media mice and combination mice/remote
controls.
Multi-Media Mouse and Combination Mouse/Remote

These types of mice are used with multimedia systems such as
the Windows XP Media Center Edition computers. Some combine
features of a mouse with additional buttons (such as play,
pause, forward, back and volume) for controlling media.
Others resemble a television/media player remote control with
added features for mousing. Remote controls generally use
infrared sensors but some use a combination of infrared and
RF technology for greater range.

Gaming Mice
Gaming mice are high-precision, optical mice designed for
use with PCs and game controllers. Features may include:

* Multiple buttons for added flexibility and functions
such as adjusting dpi rates on the fly
* Wireless connectivity and an optical sensor
* Motion feedback and two-way communication

Motion-Based Mice
Yet another innovation in mouse technology is motion-based
control. With this feature, you control the mouse pointer by
waving the mouse in the air.

The technology patented by one manufacturer, Gyration,
incorporates miniature gyroscopes to track the motion of the
mouse as you wave it in the air. It uses an electromagnetic
transducer and sensors to detect rotation in two axes at the
same time. The mouse operates on the principle of the
Coriolis Effect, which is the apparent turning of an object
that's moving in relation to another rotating object. The
device and accompanying software converts the mouse movements
into movements on the computer's screen. The mice also
include an optical sensor for use on a desktop.