Technical Computer Peripherals Mouse

The Mouse

The most common mouse used today is opto-electronic. It has a steel ball which is rubber coated and as it rotates it drives two rollers, one each for x and y displacement. A third spring-loaded roller holds the ball in place against the other two.

These rollers then turn two disks with radial slots cut in them. Each disk rotates between a photo-detector cell, and each cell contains two offset light emitting diodes (LEDs) and light sensors. As the disk turns, the sensors see the light appear to flash, showing movement, while the offset between the two light sensors shows the direction of movement.

Also inside the mouse are a switch for each button, and a microcontroller which interpret the signals from the sensors and the switches, using its firmware program to translate them into packets of data which are sent to the PC. Serial mice use voltages of 12V and an asynchronous protocol from Microsoft comprised of three bytes per packet to report x and y movement plus button presses. PS/2 mice use 5V and an IBM-developed communications protocol and interface.

1999 saw the introduction of the most radical mouse design advancement since its first appearance way back in 1968 in the shape of Microsoft's revolutionary IntelliMouse. Gone are the mouse ball and other moving parts inside the mouse used to track the mouse's mechanical movement, replaced by a tiny complementary metal oxide semiconductor (CMOS) optical sensor - the same chip used in digital cameras - and an on-board digital signal processor (DSP).

Called the IntelliEye, this infrared optical sensor emits a red glow beneath the mouse to capture high-resolution digital snapshots at the rate of 1,500 images per second which are compared by the DSP and translated changes into on-screen pointer movements. The technique, called image correlation processing, executes 18 million instructions per second (MIPS) and results in smoother, more precise pointer movement. The absence of moving parts means the mouse's traditional enemies - such as food crumbs, dust and grime - are all but completely avoided. The IntelliEye works on nearly any surface, such as wood, paper, and cloth - although it does have some difficulty with reflective surfaces, such as CD jewel cases, mirrors, and glass.

Monitor

Modem