Special Features:

(inavy), track ball; (drawing), trackball assembly 2.5 inch

Properties:

A device which includes a sphere mounted in a small open-topped box. The sphere is hand-operated by rotating it in a backward, a forward, or a sideway direction while maintaining the device in a fixed location. The movement of the sphere generates a signal which may be used to move a cursor and/or tracking symbol on the face of a display, such as a cathode ray tube; to input data into an electronic system; and/or to control the operation of a system. It may or may not include additional input devices, such as switches or variable resistors.