Re: What signals are coming out of the cable when a computer mouse is moving?

There are different types of mouses. For example, I used to use a Sun 
Workstation that has an optical mouse. However, most mouses have balls 
that rotate when you move the mouse. This is the type that I will talk 
about.

In my mouse (a Microsoft Serial Mouse, 2A), there is a ball that rotates 
when you move the mouse. The ball causes two rollers to turn, one in the 
vertical direction and one in the horizontal direction. On the end of this 
roller is a thing that looks like a gear with slots like a gear in it. 
Shining through these slots is a little laser light. As the wheel turns 
the roller and gear, the light blinks on and off. There is a receiver 
device (sort of like a little minature camera) that records the the light. 
How fast the light goes on and off tells the reciever how fast the ball is 
turning. 

This information is converted into a digital signal by chips in the mouse. 
This digital signal is transmitted to your computer which tells the 
computer how fast the ball is moving. In addition, digital signals are 
sent that tells your computer when one of the buttons is pressed or when 
it is released (after it has been pressed). (As an aside, I would add the 
computer cable that connects your mouse to the computer is a serial cable, 
which means that the data are sent one bit at a time, like the data that 
comes over the telephone lines through a modem.)

So the things that are in a mouse are:

1) The ball that rolls when you move your mouse.
2) Two rollers, one that moves when the mouse is moved up and down, and 
one that moves when the mouse is moved from side to side (of course, they 
both move when the mouse is moved diagonally).
3) Two optical sensing devices that are activated when the gears on the 
rollers turn.
4) Two buttons (the right and left mouse buttons).
5) A chip that converts the signal from the optical sensors and from the 
buttons to digital signals.
6) A board, wires and connectors to connect all this together.
7) A connector for the cable that runs to the computer.
8) A cables that runs to the computer.
9) Finally, a case to hold all of this stuff.


Here is a website with some images that may help in visualizing some of this:

http://www.4qd.co.uk/faq/meece.html