Patent ID: 7708482

Claim:
A control method for operating a printer comprising a main printer unit having a paper transportation path formed therein with an open position to enable paper to be inserted into the paper transportation path and a closed position for preventing the insertion of paper into the paper transportation path, the printer further comprising, a roll paper holder, a sheet feeding device and connector guides for said sheet feeding device configured such that only the roll paper holder or the sheet feeding device can be installed to the main printer unit at any one time, the method comprising: installing the roll paper holder in the main printer unit at a first location when the sheet feeding device is not installed for feeding roll paper to said paper transportation path; installing the sheet feeding device in the main printer unit at a second location different from the first location when the roll paper holder is not installed for feeding sheet paper to said paper transportation path; using optical sensors for simultaneously detecting if the roll paper holder is installed to the printer when power to the printer is turned on, and at the same time detecting if the sheet feeding device is not installed to the printer, and if so: determining if the paper transportation path is in the closed position; detecting a leading end and a trailing end of paper in the paper transportation path; discharging the paper from the paper transportation path when only the leading end of the paper is detected or indexing the paper in the paper transportation path when only the trailing end of the paper is detected.