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:
Jan. 21, 2003
Filed:
Aug. 03, 2000
Shiro Fujiki, Yokohama, JP;
Vertex Standard Co., Ltd, Tokyo, JP;
Abstract
A key matrix circuit has a switching circuit with a first terminal and a second terminal that are switched on and off by pressing a selection key of a plurality of selection keys arranged in an N-row-by-M-column matrix, thereby making connection to a common ground circuit when a selection key is pressed. The key matrix circuit has a first voltage-dividing circuit connected between a connection circuit that connects the first terminals of the first row and a fixed power supply voltage, and a second voltage-dividing circuit connected between a connection circuit that connects the second terminals of the first column and the fixed power supply voltage, the connection points between resistances to of the first voltage-dividing circuit being connected to the connection circuits connected to the first terminals of the other rows, and the connection points between resistances of the second voltage-dividing circuit being connected to the connection circuits of the other rows. An output voltage at the connection point between the first voltage-dividing circuit and an output voltage at the connection point between the second voltage-dividing circuit are input to a microcomputer circuit. Based on combinations of the voltage levels, the microcomputer circuit references a table prepared beforehand, so as to recognize what selection key has been pressed.