Oce 3121 Technical & Service Manual page 567

If misalignment occurs, the motor M5 is switched ON, to raise or lower the ten-
sion roller. The film will traverse to the centre, correcting the misalignment.
Correction is continued as necessary to ensure correct alignment of the film.
If the film has become displaced so much that the correction mechanism can-
not control it, 'E007' will be indicated.
Control of the alignment motor
2
The alignment motor is a stepping motor, rotated by the pulse signals A, A*,
B, B*.
510 TSM Océ 3121 Functional description