A printer (10) has a detection mechanism for detecting the absence of paper and the end position of the printhead upon start-up and reset. The detection mechanism includes a detection lever arm (16) that is spring loaded and operationally positioned in a normal state. An optical sensor (17) made up of an LED (17a) and a photo transistor (17b) that transmits light to the LED (17a), has the lower end of the detection lever arm (16) operationally positioned in the normal state, between the LED (17a) and the photo transistor (17b). The upper end of the detection lever arm (16) is urged against the paper, by the spring (15). The platen (11) supporting the paper has a groove (12) formed therein which, in the absence of paper, receives the upper end of the detection lever arm (16), causing the lower end to move from its normal position between the LED (17a) and the photo transistor (17b), the optical sensor (17) then indicating a paper-out condition. The carriage (14) for supporting and moving the printhead (22; see Fig. 5) has an activation arm (13) that moves against the detection lever arm (16) when the carriage (14) moves to the leftmost position, thereby moving the lower end of the lever arm (16) away from the normal state, the optical sensor (17) then indicating a column one position.