A modularized probe head for modularly assembling on a probe card is configured for probing a semiconductor wafer under test. A common-mode voltage of a differential signal and an average for the common-mode voltage of the differential signal are measured. In a portion of a selected period, a drain current flows into the auxiliary transistor and a signal current flowing through a signal line, which represents a current to flow into the current-driven device, is times a normal value. As a result the package construction is reinforced. A decoder or decoding function aspect of the invention processes the main layer to generate synthetic high-frequency components and combines the synthetic high-frequency components, main layer and enhancement layer to provide a decoded output signal similar to the video signal applied to the encoder. Output of sub-procedure may be formatted per a final output format, facilitating union therebetween.