detected within this section in addition to the printed product 6 fig1 b also shows the printed products 6 u2032 6 u2033 with the leading edges 8 u2032 8 u2033 and the side edges 9 u2032 9 u2033 which respectively occupy during the processing a position that differs from the position of the printed product 6 the two sensors 2 respectively form a light curtain 2 b which in part impinges on the top of the respective printed product 6 6 u2032 6 u2033 and in part also on a reflector 2 a the light rays impinging on the reflector 2 a are reflected back to the sensor 2 as a result it is possible to determine at any time which region of the respective printed product 6 6 u2032 6 u2033 is located within the area covered by the two sensors 2 each position of the leading edges 8 8 u2032 8 u2033 and thus also the position of the printed products 6 6 u2032 6 u2033 can therefore be detected in the area that is covered by the length of the two sensors 2 the measuring values are supplied via corresponding signals to an automatic controller 3 this automatic controller 3 is connected to a control 4 and the drive 5 the conveying device 13.