Computer Mice

Mice first broke onto the public stage with the introduction of the Apple Macintosh in 1984, and since then they have helped to completely redefine the way we use computers.

Every day of your computing life, you reach out for your mouse whenever you want to move your cursor or activate something. Your mouse senses your motion and your clicks and sends them to the computer so it can respond appropriately.

Developed by Agilent Technologies and introduced to the world in late 1999, the optical mouse actually uses a tiny camera to take thousands of pictures every second.

Able to work on almost any surface without a mouse pad, most optical mice use a small, red light-emitting diode (LED) that bounces light off that surface onto a sensor. In addition to LEDs, a recent innovation are laser-based optical mice that detect more surface details compared to LED technology. This results in the ability to use a laser-based optical mouse on even more surfaces than an LED mouse.

Optical mice have several benefits over track-ball mice:

· No moving parts means less wear and a lower chance of failure.

· There's no way for dirt to get inside the mouse and interfere with the tracking sensors.

· Increased tracking resolution means a smoother response.

· They don't require a special surface, such as a mouse pad.

A number of factors affect the accuracy of an optical mouse. One of the most important aspects is resolution. The resolution is the number of pixels per inch that the optical sensor and focusing lens " see" when you move the mouse. Resolution is expressed as dots per inch (dpi). The higher the resolution, the more sensitive the mouse is and the less you need to move it to obtain a response.

Most mice have a resolution of 400 or 800 dpi. However, mice designed for playing electronic games can offer as much as 1600 dpi resolution. Some gaming mice also allow you to increase the dpi on the fly to make the mouse less sensitive in situations when you need to make smaller, slower movements.

Historically, corded mice have been more responsive than wireless mice. This fact is changing, however, with the advent of improvements in wireless technologies and optical sensors. Other factors that affect quality include:

· Size of the optical sensor -- larger is generally better, assuming the other mouse components can handle the larger size. Sizes range from 16 x 16 pixels to 30 x 30 pixels.

· Refresh rate -- it is how often the sensor samples images as you move the mouse. Faster is generally better, assuming the other mouse components can process them. Rates range from 1500 to 6000 samples per second.

· Image processing rate -- is a combination of the size of the optical sensor and the refresh rate. Again, faster is better and rates range from 0.486 to 5.8 megapixels per second.

· Maximum speed -- is the maximum speed that you can move the mouse and obtain accurate tracking. Faster is better and rates range from 16 to 40 inches per second.

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.

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.

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.

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.