j-r charles asks: "I need to design a 12 key keypad that plugs into a PS2 port INSTEAD of the standard PC keyboard. Does anyone knows the protocol used by IBM, or where to find it?" So why stick with the boring old choices of 88 and 101 keys when you can build your own with as many (or as few) as you like. Has anyone built custom keyboards for their PCs? How difficult was it?