roller 106 and facing roller 107 are rotatably mounted within the housing 101 on roller axles 148 and 150 respectively to feed paper to the roller and facing roller the paper roll 102 is supported by a detachable roll axle 140 mounted externally to the housing 101 by a bracket 144 the paper passes from the paper roll into the housing through an input paper aperture 146 as the paper 103 enters the housing 101 the roller 106 and the facing roller 107 engage opposite sides of the paper 103 when the user pulls the paper and propels the paper through the printer the roller and the facing roller are rotated by their frictional engagement with the paper in this embodiment rotation of the roller 106 is transmitted to the encoder axle 113 of the rotation sensor 114 through a belt 152 to produce corresponding rotation of the encoder wheel 112 the belt 152 is positioned on a pulley 154 attached for rotation with the roller 106 rotation of the roller is then translated into an electrical signal by the rotation sensor 114 in similar fashion to that described above upon receiving the electrical signal from the rotation sensor 114 the microprocessor 116 determines the rotational angle of the roller 106 and from this determines the position of the paper 103 along the paper path 104 from the determined position of the paper the microprocessor identifies the portion of the paper to which the print elements 108 of the thermal printhead 110 are aligned as the paper 103 travels beyond the roller 106 and the facing roller 107 it passes between the printhead 110 and an engagement roller 156 the engagement roller provides pressure to the paper to maintain the paper in contact with.