In an array substrate and a display apparatus, a pixel part has a plurality of gate lines, a plurality of data lines, and a plurality of pixels electrically connected to the gate and data lines. The RF coil of the invention includes an array of patches which are capacitively coupled with each other. The engaging portion defines a recess. A bi-directional communication link extends between the remote computer and the well tree processor. The user interface is configured to receive said value from the water heater controller and to selectively illuminate a number of segmented portions representative of said value.