A hot stick testing apparatus and method including a pair of generally ring-shaped electrodes spaced from one another at a predetermined distance. The interactive charts are generated in an online portal that allows users to customize the interactive features of the chart. Through monitoring the student’s volitional or involuntary behavior, the system provides an indication on the student’s concentration level. It is also possible that some of the compressive force be transferred to the cryocooler body. The method further comprises the steps of receiving and recovering an IS-OFDM signal. Super dithering relies on both the spatial and temporal properties of human visual system, wherein spatial dithering is applied to account for human eye’s low pass spatial property, while temporal dithering is applied to achieve the quantization level of the spatial dithering.