Abstract: A system and method for selecting the active input/output port for a computer having a plurality of input/output ports of different are disclosed. The computer is in communication with and an input device connected to the computer via one of the input/output ports. The system includes an input sensor for receiving an input signal and an input device controller in communication with the input sensor and with the computer. The input device controller includes an input interface configured to receive an input signal from the input sensor and a communications processor configured to receive the input signal from the input/output ports, determine which of the input/output ports received the input signal, select the input/output port that received the input signal as the active input/output port and utilize the active input/output port for communication.

Abstract: A method and apparatus to improve the accuracy and responsiveness of computer light pens, while simultaneously reducing the associated computing overhead, is disclosed. A light pen is a device that generates an electrical signal when touched to an illuminated section of a computer screen. The position of the pen on the screen can be determined by timing relationships between the signal from the pen and the synchronizing signals being sent to the screen by its controller. The interface apparatus utilizes a pair of synchronous digital counters, one for each axis, to accumulate the timing information. A special processing method is used for the data that is read from the counters to substantially reduce the false horizontal movement normally associated with light pens. The special processing eliminates the need for frame-to-frame averaging, resulting in greatly improved responsiveness.

Abstract: An apparatus and automated process to improve the accuracy and reduce the time, cost, and effort necessary to prepare reproduction artwork for charts is disclosed. A numerically or computer controlled imaging system is used to expose photographic film or emulsion with specially prepared halftone pattern symbols. This allows a computer to be used to select both the symbol and location, instead of slow and costly manual methods. Greatest benefits accrue when the final chart is to be in color. One sheet of film per primary color is exposed using a few basic symbols, which are then combined to yield a wide range of color in the symbols of the final chart. Typically, the final product of this process is one or more sheets of monochromatic film used as masters for a color printing or color key process. Further, a method is described to avoid erroneous density (and resultant color) changes where halftone symbols overlap, as well as various other methods to improve legibility and produceability of the charts.