BRIEF DESCRIPTION OF THE INVENTION 
     The invention relates to an electronic control sewing machine, and more particularly relates to an operation mode changing system of the sewing machine, in which a machine controller, which is normally manipulated to control the rotation speed of the sewing machine, is switched to control the lateral swinging amplitude of the needle. 
     The conventional sewing machine has a knob or dial arranged on the front face thereof to be manipulated to adjust the lateral swinging amplitude of the needle. However, in order to freely and effectively control the needle amplitude during a stitching operation such as the embroidering stitching operation or other optional pattern stitching operations, it is generally required to provide the sewing machine with another operating part such as a lever suitable for manual operation to this stitching object. In the recently developed multi-functioned sewing machine such as the electronic control sewing machine, it is actually difficult to provide such an additional operating part on the front face of the sewing machine due to the problem of mounting space and the problem of structure to connect the operating part to the electronic elements printedly arranged within the sewing machine. The copending Japanese patent application No. 54-123134 discloses a technique to switch over the machine speed controller to control the needle swinging amplitude, instead of using an additional operating part. Even in this case, there is a problem to arrange a specific change-over switch in the limited space of the sewing machine. 
     The invention has been provided to eliminate the difficulties and problems of the prior art. According to the invention, a machine control power source switch is manipulated to produce a switch-over signal, which is identified in a predetermined lapse of time to avoid an erroneous operation of the sewing machine which may be caused by a simple switching operation of the power source switch. The power source switch is released to return to the initial position and is operated again to switch back the machine controller to the function controlling the rotation speed of the sewing machine. The change-over circuit is provided with transmission gates for electronically and exactly attaining this switching object. 
    
    
     BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS 
     FIG. 1 is a diagramatic control circuit of the invention, 
     FIG. 2 is a first embodiment of switch device of the invention, 
     FIG. 3 is a second embodiment of switch device of the invention, 
     FIG. 4 is an outlined representation of the switch device, and 
     FIG. 5 is a flow chart showing the control operation of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In reference to FIG. 1, a plug 1 is connected to a commercially available power source, and is connected to a connection plug 2. A switch device 3 has an operating element 4 which is moved around a pivot 5 to a first position OFF where the power source is cut off, to a second position ON where the power source is supplied and to a third position CH where the operation mode of a machine controller is changed. Namely the switch device 3 positioned at the first position opens a power source switch SW 1  and an operation mode changing switch SW 2 . The switch device 3 is moved to the second position ON to close the power source switch S 1 , and is moved to the third position CH to close the operation mode changing switch SW 2 . When released, the switch device 3 is returned to the second position, so that the operation mode changing switch SW 2  may be normally opened. 
     A control power source PW is connected to the power source plug 1 as shown. A read only memory ROM stores a number of stitch control signals and program control signals. A central process unit CPU uses the program control signals to perform the program controls. A random access memory RAM temporarily memorizes the processes and results of the performed programs, and an input and output port I/O is provided. These elements ROM, CPU, RAM and I/O constitute a microcomputer. 
     The operation mode changing switch SW 2  is closed to give a low level signal to the central process unit CPU through the input and output port I/O. A machine controller VR 1 , which is manually operated, for example, by foot, is normally used to control the rotation speed of the machine drive motor. The machine controller VR 1  is designed to be switched to control the amplitude of the needle (lateral swinging movement of the needle) in this invention. The variable resistor R 1  has one end 6 connected to the ends of transmission gates T 1 , T&#39; 4  and has the other end 8 connected to the ends of transmission gates T 3 , T&#39; 6  and the wiper 7 is connected to the ends of transmission gates T 2 , T&#39; 4 . An adjuster device VR 2  is mounted on the front face of the sewing machine and is normally used to control the amplitude of the needle (lateral swinging movement of the needle). The adjuster device VR 2  is designed to be switched to control the speed control of the machine drive motor. The variable resistor R 2  has one end 9 connected to the ends of transmission gates T&#39; 1 , T 4 , and has the other end 11 connected to the ends of transmission gates T&#39; 3 , T 6 , and the wiper 10 is connected to the ends of transmission gates T&#39; 3 , T 5 . 
     The speed control circuit SP is connected to the central process unit CPU to give and receive the speed control signals to and from the latter, and is also connected to the opposite ends of the transmission gates T 1 , T 2 , T 3 . If these transmission gates are conductive, the speed control circuit SP is connected to the machine controller VR 1 . The speed control circuit SP is also connected to the opposite ends of the transmission gates T&#39; 1 , T&#39; 2 , T&#39; 3 . If these transmission gates are conductive, the speed control circuit SP is connected to the adjuster device VR 2 . An amplitude adjusting circuit MR is connected to the central process unit CPU to give and receive the amplitude adjusting signals to and from the latter, and is also connected to the opposite ends of the transmission gates T&#39; 4 , T&#39; 5 , T&#39; 6 . These transmission gates are made conductive to connect the amplitude adjusting circuit to the machine controller VR 1 . The amplitude adjusting circuit MR is also connected to the opposite ends of the transmission gates T 4 , T 5 , T 6 , and these transmission gates are made conductive to connect the amplitude adjusting circuit MR to the amplitude adjusting device VR 2 . 
     The output of the speed control circuit SP is applied to the machine drive motor M. The input and output port I/O has an output terminal P of operation mode changing signal connected directly or through inverters N 1  -N 6  to the gates G 1 , G 2  of the transmission gates T 1  -T 6 , T&#39; 1 , T&#39; 6  as shown. If the potential of the output terminal P is high level, the transmission gates T 1  -T 6  become conductive and the transmission gates T&#39; 1 , T&#39; 6  become nonconductive. On the other hand, if the potential is low level, the state of the transmission gates is reversed. Therefore, if the potential of the output terminal P is high level, the variable resistor R 1  is connected to the speed control circuit SP, and the variable circuit R 4  is connected to the amplitude adjusting circuit MR. On the other hand, if the potential is low level, the variable resistor R 1  is connected to the amplitude adjusting circuit MR and the variable resistor R 2  is connected to the speed control circuit SP. 
     In reference to FIG. 2 showing a first embodiment of the switch device 3 of the invention, when the operating element 4, which is turnable around a pivot 12, is in the first position OFF as shown by the solid line among the predetermined positions it may take, an actuating rod 13 gives no influence to a lever 14 which is turnable around a fixed pivot 16 and is normally biased by a spring 15 in the counterclockwise direction to the most extent. The lever 14 displaces the actuator 18 of the power source switch SW 1  downwardly thereof to open the switch SW 1  by way of a movable pivot 17 to thereby open the switch SW 1 . Also in this state, the operating element 4 gives no influence to another lever 19 which is turnable around a pivot 21 and is normally biased by a spring 20 in the counterclockwise direction. The lever 19 is therefore spaced from the actuator 22 of the operation mode changing switch SW 2  to open the switch SW 2 . 
     When the operating element 4 of the switch device 3 is brought to the second position ON as shown by the broken line, the actuating rod 13 turns the lever 14 in the clockwise direction against the action of the spring 15. As a result, the actuator 18 of the power source switch SW 1  is displaced to an upper position, and the switch SW 1  is turned on and this state is maintained. However in this state, the operating element 4 is designed to give no influence to the lever 19. When the operating element 4 of the switch device 3 is brought to the third position CH as shown by the broken line, the operating element 4 turns the lever 19 in the clockwise direction against the action of the spring 20. As a result, the lever 19 pushes the actuator 22 to close the operation mode changing switch SW 2 . In this state, the operating element 4 is designed to give no influence further to the actuator 18 of the power source switch SW 1 . Then if the operating element 4 is released, it is automatically returned to the second position ON, and at the same time, the lever 19 is turned in the counterclockwise direction by the action of the spring 20. As a result, the operation mode changing switch SW 2  is opened. Another lever 23, which is turnable on a pivot 24, is operated in association with the operating element 4 to turn the lever 14 in the counterclockwise direction to thereby downwardly displace the actuator 18 of the power source switch SW 1  to open the latter when the operating element 4 is brought to the first position OFF from the second position ON. 
     In reference to FIG. 3 showing a second embodiment of the switch device 3, if the operating element 4 is brought to the second position ON from the first position OFF, a vertical link 26 is downwardly displaced by way of a movable pivot 25. Then a vertical rod 28 connected to the link 26 through a spring 27 is depressed and displaces the actuator 18 downwardly of the power source switch SW 1  to close the latter. When the operating element 4 is brought to the third position CH, the vertical rod 26 is further depressed and a magnet 30 at the lower end of the rod 26 closes a lead switch SW&#39; 2  corresponding to the operation mode changing switch SW 2  in FIG. 2 while the vertical rod 28 is prevented from further downward movement by a stopper 29 and maintains the power source switch SW 1  as it is closed. In this state, if the operating element 4 is released, it is automatically returned to the second position ON, and the vertical rod 26 is returned by the action of the spring 27 to an upper position where the magnet 30 opens the lead switch SW&#39; 2 . Since the spring 27 is at the lower end thereof connected to the rod 28, if the operation element 4 is brought to the first position OFF from the second position ON, the vertical rod 28 is displaced in the upper position and opens the power source switch SW 1 . 
     As shown in FIG. 4, the operating element 4 of the switch 3 is provided on a suitable place of a sewing machine such as on one side thereof so that the operating element 4 may be freely accessible by a machine operator. The operating element 4 is turnably mounted on the pivot 12 in the machine housing 31 and is partly projected out of the cutout 31a. The cutout 31a has three indices 33 provided on one side thereof representing the first, second and third positions OFF, ON, CH to be taken by the operating element 4. The operating element 4 has three offset indices 32 each to be in alignment with each of the indices 33 on the machine housing by operation of the element 4 so that the latter may take the three positions selectively and exactly. 
     In reference to FIG. 5 showing the flow chart for explanation of the operation of this invention; If the switch device 3 is brought to the second position ON from the first position OFF, the power source switch SW 1  is closed and the central process unit CPU starts to make a program control. Namely in a predetermined lapse of time WAIT after the power source switch SW 1  is closed, it is discriminated if the switch device 3 has been brought to the third position CH. This predetermined lapse of time is provided in such a sense that the erroneous operation of the switch device 3 may not be detected in the program. Namely in case the switch device 3 is brought to the third position by error in the course of displacement of the switch device 3 from the first to the second position, the third position CH is not detected if the switch device 3 is instantly released. If the switch device 3 is not at the third position, the central process unit CPU produces a high level signal at the terminal P. Then the transmission gates T 1  -T 6  become conductive and the transmission gates T&#39; 1  -T&#39; 6  become nonconductive. As a result, the speed control circuit SP is connected to the machine controller VR 1  and the amplitude adjusting circuit MR is connected to the amplitude adjusting device VR 2 . This may be called A-MODE and is separately indicated, and simultaneously the high level at the terminal P (A-MODE) is discriminated. Thus it becomes possible to control the rotation speed of the machine drive motor by manipulation of the machine controller VR 1 , and also to adjust the needle swinging amplitude by manipulation of the amplitude adjusting device VR 2 . 
     If the switch device 3 is brought to the third position CH, the operation mode changing switch SW 2  is closed and produces a low level signal which is detected by the central process unit CPU, and the terminal P of the CPU becomes a low level. Then the transmission gates T 1  -T 6  becomes nonconductive and the transmission gates T&#39; 1  -T&#39; 6  become conductive. Thus the speed control circuit SP is connected to the amplitude adjusting device VR 2 , and the amplitude adjusting circuit MR is connected to the machine controller VR 1 . This may be called B-MODE and is so indicated. As a result, it becomes possible to adjust the needle swinging amplitude by manipulation of the machine controller VR 1 , and to control the rotation speed of the machine motor M by manipulation of the amplitude adjusting device VR 2 . In this case, if it is necessary to control the rotation speed of the machine motor M by manipulation of the amplitude adjusting device VR 2 , the amplitude adjusting device VR 2  may be fixed to make a constant speed control of the machine drive motor M. Subsequently if the switch device 3 is brought to the third position CH again, the same mode of operation is repeated from the point RE through the repetition point RET.
In a sewing machine having a machine controller for controlling the rotational speed of the machine and a needle amplitude, adjusting device, a machine control power source switch is provided which is manipulated to produce a switch-over signal, which is identified in a predetermined lapse of time to avoid an erroneous operation of the sewing machine which may be caused by a simple switching operation of the power source switch. The power source switch is released to return to the initial position and is operated again to switch back the machine controller to the function controlling the rotation speed of the sewing machine. The change-over circuit with transmission gates is provided in the sewing machine, which is electrically connected to the amplitude adjusting device and the machine controller and to the control power source switch, respectively.