The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 19, 1977
Filed:
Nov. 25, 1975
Wilbur E DuVall, Victorville, CA (US);
Xerox Corporation, Stamford, CT (US);
Abstract
A keyboard encoding system which utilizes electronic hysteresis to prevent undesired key stroke encoding. The output of a capacitive switch matrix is supplied to a sense amplifier which has its sensitivity increased if a particular switch of the switch matrix was closed the last scan cycle. The status of the switches of the switch matrix during the last scan cycle is provided by a shift register having a number of stages equal to the number of switches of the matrix. The sense amplifier includes a comparator which receives an input indicative of the state of a particular matrix switch during the present scan cycle and an input from the shift register indicative of the status of the particular matrix switch the previous scan cycle. If the input from the shift register is high, the sensitivity of the sense amplifier is increased.