Programmable acceleration is the controller's ability to limit the rate at which speed is allowed to change. Transistors are very quick and can switch from full forward power to full reverse (a worse case scenario) in a matter of microseconds. Because of the motor's and the robot's inertia, such changes will result in a very high, sudden and potentially damaging overcurrent inside the controller. Such changes can also create significant mechanical stress to the robot's structure as well. The AX2550's current limiting feature is one way the controller can limit the effects of such changes. With programmable acceleration, the controller will take the user's command and automatically "smooth" the change. In the full forward to full reverse example, the controller will gradually reduce the speed to 0 and then accelerate to full reverse.