Keyboard without ghost keys

Details Keyboard without ghost keys Keyboard without ghost keys

2008-05-20

2008-05-20

Zimmerman, Brian (Department: 2612)

Coded data generation or conversion

Bodily actuated code generator

Including keyboard or keypad

C341S022000, C714S813000

Reexamination Certificate

active

07375655

ABSTRACT:
A keyboard without ghost keys has a circuit which includes a microprocessor in which a plurality of I/O lines form a keyboard scanning matrix. Two of the I/O lines on the matrix cross to define a plurality of signal switches. The microprocessor is electrically connected to a primary level resistance and a reference potential to determine the ON condition of the signal switches. Each signal switch further is electrically connected to at least one secondary level switch which is electrically connected to the primary level switch in a serial manner. When a user depresses any three signal switches on the rectangular angles of the keyboard scanning matrix, the connecting primary level resistance and the secondary level resistance form a new level resistance. The new level resistance and the current flowing to the keyboard scanning matrix are processed to get a potential smaller than the reference potential, thereby to eliminate the phenomenon of ghost keys.

REFERENCES:
patent: 4633228 (1986-12-01), Larson
patent: 5448236 (1995-09-01), Shiga
patent: 486661 (2002-05-01), None
patent: 578088 (2004-03-01), None

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