04012588 is referenced by 64 patents and cites 6 patents.

An apparatus for determining the position of a movable element or stylus which is movable in a data space. In accordance with the invention there are provided first and second spaced receivers, each receiver comprising a hollow shell of piezoelectric material, which may be cylindrical or spherical in shape, and resilient conductive means coupled across the inner and outer surfaces of the shell. Means are provided for periodically generating a source of sound waves for travel between the stylus and the first and second receivers. Timing means are coupled to the receivers and synchronized with the generation of the sound waves for measuring transit time of the sound waves between the source and receivers. Computing means are employed to determine the positional coordinates of the stylus in a desired coordinate system, such as rectangular coordinates. In an embodiment of the invention the first and second receivers have conductive mesh loaded within the shell and in contact with the inner surface of the shell. In this embodiment a spring contact is coupled to the outer surface of the shell. In an embodiment of the invention the movable element or stylus is passive and means are provided for periodically generating sound waves at a source position spaced from the movable element. This eliminates the need for an "active" stylus and the problems associated therewith.

Title
Position determining apparatus and transducer therefor
Application Number
5/608917
Publication Number
4012588
Application Date
August 29, 1975
Publication Date
March 15, 1977
Inventor
Joseph A Howells
Danbury
CT, US
Robert L Davis
Prospect
CT, US
Agent
Martin Novack
Assignee
Science Accessories Corporation
CT, US
IPC
G08C 21/00
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