04814552 is referenced by 129 patents and cites 4 patents.

This invention is an input device, or stylus, for entering hand drawn forms into a computer comprising a writing instrument, a pressure switch for determining whether the instrument is in contact with the writing surface, an acoustic transmitter for triangulating the position of the stylus on the surface, and a wireless transmitter for transmitting data and timing information to the computer. In operation, the stylus transmits an infra red signal which the system receives immediately, and an ultra sound pulse which two microphones receive after a delay which is a function of the speed of sound and the distance of the stylus from each microphone. From this information the system can calculate the position of the stylus. Switches for indicating functions are mounted on the stylus. Multiple stylusses can be used, each transmitting a distinctive identification code so that the system can determine which stylus is the signal source.

Title
Ultrasound position input device
Application Number
7/127730
Publication Number
4814552
Application Date
December 2, 1987
Publication Date
March 21, 1989
Inventor
J Courtenay Heater
Cupertino
CA, US
Mark J Stefik
Portola Valley
CA, US
Agent
Robert E Cunha
Assignee
Xerox Corporation
CT, US
IPC
G08C 21/00
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