Abstract: Illumination color for a dedicated legend display area of an illuminated pushbutton switch may be programmed by controlling application of the driving voltage to one of two or more different groups of interleaved LEDs alternately illuminating the display area. Each of the different LED groups illuminates the display area with a different color, produced by different color LEDs, filtering of individual LEDs within each group, or dip-coating the LEDs. Application of the driving voltage to different switch input pins causes the legend to be illuminated by different LED groups in different colors, reflecting different conditions.

Abstract: Illumination sources, each including at least one light emitting diode, are connected either in series or in parallel by a switching circuit, depending upon an applied input voltage. The switching circuit switches the illumination sources from series- to parallel-connection, or vice versa, when the applied input voltage crosses a threshold value in traversing the operating range of applied input voltages. Because the light emitting diodes within the illumination sources are switched from series to parallel connection at a defined kickover point, the voltage-luminance characteristic changes on opposite sides of the kickover point. The resulting overall voltage-luminance characteristic has greater variability in luminance across the entire operating range of applied input voltages, and luminance-variance is not limited to only a portion of the operating range.

Abstract: Illumination sources, each including at least one light emitting diode, are connected either in series or in parallel by a switching circuit, depending upon an applied input voltage. The switching circuit switches the illumination sources from series- to parallel-connection, or vice versa, when the applied input voltage crosses a threshold value in traversing the operating range of applied input voltages. Because the light emitting diodes within the illumination sources are switched from series to parallel connection at a defined kickover point, the voltage-luminance characteristic changes on opposite sides of the kickover point. The resulting overall voltage-luminance characteristic has greater variability in luminance across the entire operating range of applied input voltages, and luminance-variance is not limited to only a portion of the operating range.

Abstract: Multi-color illumination for a single display is achieved by utilizing an array of white light emitting diodes to produce illumination optically filtered by separate filters to produce the two or more desired output illumination colors at a desired luminance when the full rated voltage is applied to the light emitting diodes. Since all of the light emitting diodes have the same bandgap, voltage-controlled dimming produces uniform luminance changes for all colors as the voltage is reduced. A single voltage-controlled dimming driver circuit design and a single control voltage may therefore be utilized to achieve desired and uniform dimming characteristics independent of output illumination color.

Abstract: A zener diode is connected in parallel with sets of series-connected light emitting diodes with a reverse forward bias orientation. The threshold voltage of the zener diode is matched to equal, or be just slightly greater than, the forward voltage drops for the light emitting diodes at maximum current. During normal operation, therefore, the zener diode draws virtually no current. Upon failure of one of the light emitting diodes, the zener diode conducts without increase in the applied voltage, providing an alternate current path maintaining circuit integrity so that other sets of light emitting diodes connected in series within the circuit continue to illuminate.

Abstract: To prevent inadvertent illumination of a light emitting diode (or set of light emitting diodes) by stray currents at extremely low levels, a quiescent current limiting resistive load is connected in parallel with the light emitting diode, sized to conduct a desired minimum current at the lowest forward voltage drop at which the light emitting diode is expected to properly illuminate. Rather than connecting the resistive load across the input/output ports of the driver circuit, in parallel with any biasing resistance and the light emitting diode, the load is connected directly in parallel with the light emitting diode. Additional current through the quiescent current limiting resistive load as the voltage across the input/output ports increase is thus effectively capped by the maximum forward voltage drop across the light emitting diodes.

Abstract: Illumination sources, each including at least one light emitting diode, are connected either in series or in parallel by a switching circuit, depending upon an applied input voltage. The switching circuit switches the illumination sources from series- to parallel-connection, or vice versa, when the applied input voltage crosses a threshold value in traversing the operating range of applied input voltages. Because the light emitting diodes within the illumination sources are switched from series to parallel connection at a defined kickover point, the voltage-luminance characteristic changes on opposite sides of the kickover point. The resulting overall voltage-luminance characteristic has greater variability in luminance across the entire operating range of applied input voltages, and luminance-variance is not limited to only a portion of the operating range.

Abstract: A zener diode is connected in parallel with sets of series-connected light emitting diodes with a reverse forward bias orientation. The threshold voltage of the zener diode is matched to equal, or be just slightly greater than, the forward voltage drops for the light emitting diodes at maximum current. During normal operation, therefore, the zener diode draws virtually no current. Upon failure of one of the light emitting diodes, the zener diode conducts without increase in the applied voltage, providing an alternate current path maintaining circuit integrity so that other sets of light emitting diodes connected in series within the circuit continue to illuminate.

Abstract: Illumination sources, each including at least one light emitting diode, are connected either in series or in parallel by a switching circuit, depending upon an applied input voltage. The switching circuit switches the illumination sources from series- to parallel-connection, or vice versa, when the applied input voltage crosses a threshold value in traversing the operating range of applied input voltages. Because the light emitting diodes within the illumination sources are switched from series to parallel connection at a defined kickover point, the voltage-luminance characteristic changes on opposite sides of the kickover point. The resulting overall voltage-luminance characteristic has greater variability in luminance across the entire operating range of applied input voltages, and luminance-variance is not limited to only a portion of the operating range.

Abstract: To prevent inadvertent illumination of a light emitting diode (or set of light emitting diodes) by stray currents at extremely low levels, a quiescent current limiting resistive load is connected in parallel with the light emitting diode, sized to conduct a desired minimum current at the lowest forward voltage drop at which the light emitting diode is expected to properly illuminate. Rather than connecting the resistive load across the input/output ports of the driver circuit, in parallel with any biasing resistance and the light emitting diode, the load is connected directly in parallel with the light emitting diode. Additional current through the quiescent current limiting resistive load as the voltage across the input/output ports increase is thus effectively capped by the maximum forward voltage drop across the light emitting diodes.

Abstract: Illumination sources, each including at least one light emitting diode, are connected either in series or in parallel by a switching circuit, depending upon an applied input voltage. The switching circuit switches the illumination sources from series- to parallel-connection, or vice versa, when the applied input voltage crosses a threshold value in traversing the operating range of applied input voltages. Because the light emitting diodes within the illumination sources are switched from series to parallel connection at a defined kickover point, the voltage-luminance characteristic changes on opposite sides of the kickover point. The resulting overall voltage-luminance characteristic has greater variability in luminance across the entire operating range of applied input voltages, and luminance-variance is not limited to only a portion of the operating range.

Abstract: Disclosed are indicia display devices that are sunlight readable and which comprise a lens system having one or more body portions each of which provides a transparent internal light reflecting medium interposed between a light receiving surface and a light transmitting surface; a legend plate disposed to receive light from the light transmitting surface, with the legend plate being a laminate made up of mutually bonded elements including one or more filters; and a light source disposed to supply light to the light receiving surface. Various specific configurations of the legend plate are disclosed.