10 includes a microprocessor and a read only memory rom 8 for example an eprom or prom machine related geometrical data are placed in the form of binary coded numbers in the read only memory 8 the machine related geometrical data are understood to include 1 length measurements with respect to the point of penetration of the sewing needles 13 which define the arrangement in space of the feed station located in front of the point of sewing in the vicinity of which customarily within 180 mm the pocket slash to be sewn can be placed in the case of pocket slashes without a flap this region may be defined by two marker lights arranged in front of the place of sewing in the case of pocket slashes with a flap this region may be defined by mechanical stops one of which serves as a stop point for the front edge of the flap and the other as a stop point for the rear edge of the flap 2 length measurements with respect to the point of penetration of the sewing needles 13 defining the arrangement in space of the center knife 14 3 length measurements with respect to the point of penetration of the sewing needles 13 defining the arrangement in space of the angle cutting knives 15 and 36 referring to fig4 for sewing pocket slashes with a flap a photoelectric cell 11 is provided a given distance in front of the sewing needles 13 the front and rear edges of the flap are scanned with the cell 11 and then the length of the pocket slash seam to be sewn is derived precisely from the measured length of the flap the scanning signals from the photoelectric cell.