Coded data generation or conversion – Bodily actuated code generator – Including keyboard or keypad
Reexamination Certificate
1999-01-11
2001-09-11
Horabik, Michael (Department: 2735)
Coded data generation or conversion
Bodily actuated code generator
Including keyboard or keypad
C341S020000, C341S026000, C178S01700D, C340S870030
Reexamination Certificate
active
06288652
ABSTRACT:
TECHNICAL FIELD
This invention relates to the field of keypad apparatus that represents the switch states as a binary number for controlling locking and unlocking functions.
BACKGROUND OF THE INVENTION
The automotive industry is using password entries from five-switch keypads to supplement conventional key-entry and wireless arrangements to allow drivers and passengers to lock and unlock the vehicle doors. Presently, existing keypad apparatuses utilize an individual wire on one side of each normally open switch contact, and a common return wire on the other side. These keypads commonly include an internal lamp for backside illumination of switch legends. The lamp has its own wire for power, and either shares a return wire common to the switches, or has a dedicated return wire. This results in a seven or eight wire interface to the keypad.
Multiplexing the individual switch contact wires reduces the total number of wires of the assembly. The apparatus requires three bits of information to distinguish the five individual switch closure states, and a sixth state where no switch is closed. A keypad apparatus using a common return wire for the three information bits and for a light source requires only a five wire interface. Where the light source has a dedicated return wire, six wires are required. A five or six wire interface keypad apparatus can be made for lower cost than a seven or eight wire interface keypad apparatus.
U.S. Pat. No. 4,502,040, issued to Castel on Feb. 26, 1985, discloses a keypad apparatus that multiplexes four switches onto two wires. In Castel, each switch closure creates an electrically unique connection between the two multiplex wires. The characteristics are of an open circuit, short circuit, forward biased diode, and reverse biased diode, respectively. The keypad apparatus requires successive applications of two reverse electrical voltages to distinguish among the four characteristics. Castel is not well suited for current automotive keypad applications because it can distinguish only four switches, one of the four switches must be closed at all times, and it cannot distinguish simultaneous dual switch closures from single switch closures.
DISCLOSURE OF THE INVENTION
The present invention provides a five-switch keypad apparatus having four diodes that multiplex the switch contacts onto three sense terminals. The three sense terminals create a binary code that defines eight possible switch states. The eight states are used to indicate each individual switch closure, a lack of switch closures, and two simultaneous dual switch closures. In an application, a decoder, connected to the three sense terminals, converts the sequence of binary codes into three control signals. The three control signals can control a door lock, a trunk lock and an automatic lock function.
Accordingly, an object of the present invention is to provide a five-switch keypad apparatus that represents switch states as three bits of information.
This and other objects will become more apparent from a reading of the detailed specification in conjunction with the drawings.
REFERENCES:
patent: 3792466 (1974-02-01), Arnold
patent: 4042777 (1977-08-01), Bequaert
patent: 4242676 (1980-12-01), Piguet et al.
patent: 4417247 (1983-11-01), Dressler
patent: 4502040 (1985-02-01), Castel
patent: 4655621 (1987-04-01), Holden
patent: 4673933 (1987-06-01), Bauer
patent: 4680572 (1987-07-01), Meguire
patent: 4906993 (1990-03-01), Freeman et al.
patent: 5424731 (1995-06-01), Kronberg
patent: 1492538 (1977-11-01), None
Aaron Mark Christian
Bedi Sukhminder Bobby
Buchanan Michael J.
Jaworski David Joseph
Slotkowski Kenneth George
Ford Global Technologies Inc.
Horabik Michael
Stec Jennifer M.
Wong Albert K.
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