Patent ID: 7775730

Claim:
A method for detecting failure of a paper detector in a roll paper printer in which roll paper from a roll paper compartment is guided along a paper transportation path which is in an open state when a cover to the roll paper compartment is in an open state, the method comprising steps of: (a) detecting if the cover is in an open or closed state; (b) starting counting the time when step (a) detects the cover is in an open state; (c) detecting, using the paper detector, if roll paper is present indicating a paper state or is not present indicating a no-paper state in the paper transportation path; and (d) determining that the paper detector is faulty based on the detection result from step (c); wherein (d1) if the cover open state continues for a first set time period or longer, step (d) determines that the paper detector is faulty if the paper detector has not detected a change in state to a no-paper state within the first set time period.