The tracker ball was developed for military and industrial use and can give two dimensional manipulation which provides both fast movement and good fine control. It measures approximately 200mm by 110mm, is no taller than your Beeb, and does not look out of place beside it. The 'ball' part is about two-thirds the way up the face of the device, which is sloped so that the palm of your hand sits comfortably on the top and your fingers can easily manipulate the ball. Just above the ball are three buttons that can be put to various uses.

It plugs into the user port and, for the technically minded, relies on the use of the two interrupt lines. Marconi provides various pieces of software that allow you to use the Tracker Ball in different ways, plus a drawing/artist program — but more on that later.

For a review go to http://chrisacorns.computinghistory.org.uk/docs/Mags/AU/AU_Sep85_MarconiRB2.pdf

The RB2 was introduced in September 1985 and cost £59.00. Our RB2 has a  model number of RB2/PC-1 and was kindly donated by Netherhall School, Cambridge.