a gauge which uses a prism or other type of reflector to illuminate a single graphic or icon on a dial such that only one graphic on the dial is shown during the operation of the gauge . all of the remaining graphics have a dead front appearance , and cannot be viewed , such that the gauge presents only one discrete value at a time . the dial is beneath a lens , and the prism is beneath the dial . an actuator is mounted to a pcb , and an led is also mounted to the pcb to allow the prism to transmit light to the desired area of the dial . the dial also includes a central graphic , or icon , and the gauge is able to display different values , while the central graphic remains constantly illuminated in the center of the gauge .