Before the motors will engage, you must press the yellow button in order to allow electricity to go to the servo motors. You must press this button before the computer can send signals to drive the machine. The big red button cuts the electricity off to the servo motors. In an emergency you can whap it or slap it to make the sew head stop moving. It’s specially designed so re-engage after pressing the red button you will have to pull out the red button and rotate it about a 1/4 turn. After that, you can then press the yellow button to allow the signals to flow to the servos again.