Abstract: A self-tuning digitizer control circuit and method which employs a tunable excitation source instead of a tunable front end. In addition, the digitizer control circuit includes a stylus for sensing the excitation signal, and a circuit for processing the information signal from the stylus, including a narrow bandpass filter for passing the frequency of the excitation signal and minimizing the passage of extraneous noise. A controller determines the location of the stylus on the active surface of the digitizer and control operation of the circuit. The excitation source includes, in the preferred embodiment, a tunable divide-by-n circuit employing an 8-bit latch, an 8-bit counter, and a state machine. A nonvolatile memory stores the most recent value for the divisor value n. Provision is also made for a tuning method for the divide-by-n circuit.

Abstract: A digitizer screen and method of making. A coated conductive plastic film is perforated and is used in conjunction with a glass or other panel to provide a screen which may be used in an electronic digitizer for converting the position and movement of a stylus or other device on the screen to electrical signals representative of such positioning and movement. The perforated coated conductive plastic film may be laminated to the glass panel to form an integrated structure which does not require the use of masking and etching or similar processes to produce a desired apertured matrix pattern in the plastic film. Various arrangements of the plastic film are disclosed which facilitate the connection of the apertured portion of the plastic film to associated electronic components.

Abstract: A handwriting capture device which employs a highly sensitive digitizer to accurately capture signature information entered using a writing force greater than or equal to a predetermined writing force. The handwriting capture device includes a housing having a top surface, a resistive membrane digitizer mounted in the top surface and having a low pattern density, a layer of urethane rubber for frictionally holding the receipt in place, circuitry for processing digitizer information, a clamp for retaining a receipt in place over the digitizer during movement of the device, and circuitry for sensing the presence of the receipt and for activating data capture by the digitizer when the receipt is positioned under the clamp. In the preferred embodiment, the clamp also serves to minimize finger contact with the digitizer.

Abstract: A method of producing an image drive signal which is free of skew. Disclosure is made of a point of sale merchandising system having a transparent digitizer mounted on an LCD module. A stylus is used to draw a signature on the digitizer, and the signature is displayed on the LCD module in registration with the moving stylus. Skew effects are eliminated by performing a mapping transformation using a set of 6 transformation constants. These constants are derived from data obtained while placing the stylus over three reference spots on the display.

Abstract: A system and apparatus for compressing redundant and non-redundant binary data generated as part of an operation of a time and attendance terminal in which the data represents the time an employee is present during working hours. The first data entry includes the date and the time the employee operates the terminal together with other data identifying the employee which is stored in a circular buffer. The time of day data includes the hour and the minutes of the keyboard operation. Subsequent data entries include redundant data such as the date and the hour of the terminal operation which may not change and non-redundant data such as the minutes that pertain to the terminal operation together with data identifying the operator. After the redundant and non-redundant data of the first data entry are stored, only the non-redundant data of each subsequent data entry is stored.