Keyboard wedge

From the WiseGeek site:

"A keyboard wedge is an interface which allows a non-keyboard device to plug into a computer as though it were sending keyboard data. Since most data-entry software is set up to take data from a keyboard, it is necessary to use a keyboard wedge if you want to plug in a peripheral such as a barcode scanner or magnetic strip reader and have it send information to the program. A keyboard wedge is so called because the physical version "wedges" between the keyboard and the computer. The keyboard is plugged into the wedge, which in turn is plugged into the computer, so that data may be inputted through either the keyboard or the other peripheral."