Although it may seem overwhelming at first glance, the KEYKatcher is a very simple device to understand.
The KEYKatcher is about two inches long, and about 1/2 inch in diameter.  Inside the device, there is a microcontroller, and a non-volatile memory chip.  The microcontroller interprets data (keystrokes) as they are typed and the non-volatile memory stores all of the data (see Figure 2).
To install the KEYKatcher, all you need to do is plug it in between your keyboard cable and your computer.  Once you do this, it is ready to record (see Figures 1 and 5).   Optionally, use a piece of heat-shrink tubing to attach the KEYKatcher to the keyboard cable.  This will ensure that the KEYKatcher cannot be removed.

Figure 2 - KEYKatcher block diagram

When you have recorded some data, and would like to retrieve it, simply open up any text editor or word processing program (Microsoft Notepad is recommended).  Type in your secret password.  As soon as your password has been correctly entered, a menu will be displayed on your screen, giving you several options, including:  View Memory, Erase Memory, Disable recording, and so on.   As soon as the 'View Memory' option has been selected, every word that has been typed on your computer will be displayed for you to see!

Figure 3 - Inside the KEYKatcher