Abstract: A loop-powered, backlit liquid crystal display (LCD) responds to a current instrumentation loop for providing a current representative of the value to be measured and an LCD for displaying the measured value. A light-emitting diode (LED) circuit, which includes an LED disposed proximate to the LCD, is interconnected with, and driven by, the current of the current instrumentation loop for backlighting the LCD.

Abstract: A liquid crystal analog display device that displays along a predetermined path defined by a path outline. It includes a backplane defining the path outline; a plurality of display segments disposed along the path; a display segment backplane; a plurality of outline segments associated with the display segments for further defining the path outline; means for applying an electric potential to the display and outline segments; means for applying an electric potential to the path outline backplane so that there is an a.c. field across the path outline segment and the path outline backplane sufficient to maintain the path outline image; and means for selectively applying an electric field across the display segments and the display segment backplane for establishing an analog image display. There is also disclosed means for applying an electric potential to the backplane defining picket outlines so that there is an a.c.

Abstract: An AC coupled LCD annunciator control system including a primary backplane electrode associated with the primary character segments, an annunciator backplane electrode associated with the annunciator segments, a backplane drive for providing a drive signal for the primary backplane electrode, and a capacitor for coupling the drive signal to the annunciator backplane electrode; a plurality of annunciator segments; a resistor interconnected between each annunciator segment and the annunciator backplane electrode; and means for selectively switching the impedance level of each said annunciator segment from a level which is above that of the resistor to a level which is below that of the resistor to provide at the lower impedance condition an AC signal between the selected annunciator segment and the annunciator backplane electrode to actuate that selected annunciator segment.