Embodiments consistent with the present invention may be used to provide accurate view-through conversion information, even in the absence of impression cookies. The attachment includes a working head and a coupling member which is joined to the working head and connectable to the toothbrush handpiece by positive andor frictional engagement. The piston rod has a projection which is adapted to mate with a recess in the front piston to provide an interlocking between the two components. The timing when data is written by the write head is determined by adding said distance to the position where the data is written. A delivery unit having the form of a gripper holding a set of filter segments after taking it over from a out-feeding unit, a sensor detecting the lack of a filter rod in the flute of the drum is situated, in the zone of the out-feeding path for sets of filter segments at least one second sensor confirming readings of the first sensor. The differential amplifier includes a differential pair of transistors that have a pair of body terminals coupled to the output node of the common mode voltage inversion circuit.