Some manual mechanical calculators can perform the automatic division. The operation is performed without any attention from the operator who turns the crank permanently in the same direction until the end of calculation. Several different techniques are used.
The cancelled underflow
In the technique of "cancelled underflow ", when an underflow appears in the accumulator (issuing from a subtraction in excess), the mechanism swaps automatically to the addition mode and the following cranck turn cancels the previous cycle. Then the carriage shifts to the next decimal position and the calculator goes back in subtractive mode (Madas, Hamann, Rheinmetall...).
The oscillating division
In the method known as "oscillating division", when an underflow appears in the accumulator, the carriage shifts to the next position without correction of the last cycle and the calculator swaps to the additive mode. It remains in this mode until an overflow appears. At this time the carriage shifts again to the next position and the calculator swaps in subtractive mode, and so on until the end of the operation. Compared to the cancelled systematic underflow, this procedure reduces by a factor two the number of reversing the direction of rotation, however if one wishes to stop division on an odd position of the carriage, the result is given by excess and the remainder appears in its complementary form (Mercedes, Diehl..).
The division stop
Another technique known as "division stop" consists in blocking the mechanism as soon as the corrective cycle is carried out. To continue the calculation, it is enough to shift the carriage to the next decimal position, then the mechanism swaps to the subtractive mode . This method is similar to the cancelled systematic underflow method except that a pause is done between each decimal place (Contex..).