Disclosed is a communication apparatus having a small-scale circuit used for modulation. Systems comprise client and server computers attached to a communication network. The calibrator measures the concentration of elemental mercury Hg02 within the stream and calculates a difference between the known elemental mercury concentration, Hg01 and the reduced concentration Hg02. Even though the abrasion occurs by using the blade, since the sawlike or wavy edge part is semipermanently maintained, the cutting ability is not reduced. This method allows formation of thermal silicon nitride that is thick enough for a FET gate dielectric, but has a low thermal budget. When coordinates on the image are sequentially designated by an input device, the CPU sequentially compares the locations specified by the designated coordinates with those of checking points stored in the image location table.