A low pass filter smooths a voltage corresponding to a least significant bit of a digital image signal outputted from an AD convertor, and outputs the smoothed voltage to a sample-and-hold circuit. Using the invention, an HTML file for a dynamic web page need be read and parsed only once throughout the life of the server. If a fault is indicated, the component control signal has a value between high and low states, and otherwise the state of the component control signal equals the state of the second control signal.