Abstract: An image signal captured by a monitor camera is input to an image processing device, displayed on a multiwindow display, and stored in a main storage device. A sound signal collected by a mike is input to a sound processing device, regenerated through a speaker, and stored in the main storage device. Process data transmitted from a process data controller are displayed on the display and stored in the main storage device. If an abnormal condition is detected in a monitored object, often the data stored in the main storage device before or after the abnormal condition has occurred are saved into a auxiliary storage device. When data are regenerate, the saved data are synchronized with each other while being regenerated on the display and through the speaker.