the shape of the needle hole of needle plate 34 is effectively changed to a semicircular needle hole 35a thus needle bar 6 is set at the middle basic line and the needle hole of needle plate 34 is set to correspond to straight stitching the control circuit then registers the change from zigzag stitching to straight stitching and the process begins once again if the same stitch is again selected the relationship between needle position and the needle hole in needle plate 34 is the same since the previous stitch was straight thus recess 41a of the amplitude link 41 may be retained at the middle of its turning range and pulse motor 39 therefore does not change needle position the sewing machine is then accelerated from low speed to the high speed the clutch solenoid 42 is not needed and it is thus deenergized in this case engaging pin 46a of bushing 46 is not located in notch 50b so switching arm 50 is limited in leftward movement by pin 46a even when clutch solenoid 41 is deenergized therefore the amplitude link 41 and the switching arm 50 are still connected to the clutch needle bar 6 and needle hole in needle.