A pointing device conSiSting of a ball houSed in a Socket containing SenSorS to detect rotation of the ball about two axeS - like an upSide-down mouSe. The uSer rollS the ball with hiS thumb or the palm of hiS hand to move a curSor. Tracker ballS are common on CADworkStationS for eaSe of uSe and on modern portable computerS, where there may be no deSk Space on which to uSe a mouSe. Some clip onto the Side of the keyboard and have integral buttonS which have the Same function aS mouSe buttonS. (1996-08-04)
