A method of obtaining a more accurate estimate of a signal correction parameter in sequencing-by-synthesis operations, such as incomplete extension rates, carry forward rates, andor signal droop rates. The first conveying section includes a first conveying roller arranged downstream in a sheet conveying direction of the color erasing section and conveys the sheet at the first speed. A conveyance roller conveys the recording medium in a conveyance direction. Test circuitry, which is coupled to the input, upon receipt of the battery-post-adapter-connection indicator, determines whether or not the first battery post adapter and the second battery post adapter are faulty.