The PCB transmission system is driven by a stepper motor. The stepper motor is more "smart" than a normal DC motor. It divides the PCB transmission process into two phases. In the first phase, it transfers the PCB at full speed, when the PCB is close to the bezel. The stepper motor will slow down to prevent the PCB from hitting the bezel. Under this new transmission system, each PCB can be transmitted at the fastest speed.