The present invention relates generally to mill blank constructions to facilitate the manufacture of dental restorations. A Y-matrix unit 112 and a C-matrix unit 113 convert an original color obtained from image-sensing devices 111 to luminance signals and color-difference signals. A first group of communication resource units are selected from the communication resource in ascending order and assigned to a first group of communications devices to perform information transmission operations in a first time period. The plurality of connection ports is disposed on the second face. The valve is opened when the position of the float is in a predetermined position within the tube so that the mass or volume of the drained liquid is known. The body of each of the rails includes a slot, and internal passageway, and a boring.