mounting of the sensors 13 at regular spacings on the toothed belt 14 which is driven in rotation by the drive pulley 15 and which passes around the idle pulley 15 39 the distance between two successive sensors must be equal to the total distance between the marks on the program card 42 fig6 shows the means for driving the drive pulley 15 which drives the sensors 13 by way of the toothed belt and the idle pulley 15 39 the drive pulley 15 is fixed on the shaft 16 which is itself fixed with respect to the dog clutch carrier 17 pivotally mounted on the carrier 17 are two levers 18 comprising two arms which form between them an angle which depends on the two ratios to be provided and which are provided at each of their ends with a tooth whose shape is adapted to that of the teeth of the hollow gears into which they may engage a ring 19 which is slidable on the levers 18 may occupy one of three positions 19 39 19 34 and 19 34 39 in position 19 39 the ring 19 presses the levers 18 by way of springs 20 and forces them into engagement with the hollow pinion 22 of the wheel 24 causing the teeth to bottom against each other to eliminate play as the hollow pinion 22 is fixed with respect to the shaft 23 with movement being imparted to the shaft 23 by the knitting carriage the shaft 16 is now directly fixed with respect to the shaft 23 and rotates at the same speed this possibility is used for controlling the sensors for reading squared program cards and when the knitting carriage is displaced by the distance between two needles the sensors are displaced.