A POS-based system including a system housing having a horizontal housing portion and a vertical housing portion. Each of the two separation tubes is made of a wear-resistant plastic, thereby eliminating noise due to friction when the two tubes are rotated relatively by the door plate. The calcsheet may include multiple columns of vertical calculations. For each possible new state, logic 68 determines the errors of the two transitions leading from old states to that new state, adds them to the accumulated errors of those two old states, and determines the smaller of the two sums.