Abstract: An analog automatic slowdown control system is described for determining the optimum instant of time to initiate slowdown, for a process line in which a coil of material is being unwound from a mandrel at a linear speed. Using the intelligence derived from the linear speed and the speed of the unwind reel, signals are derived for: the instantaneous diameter, the desired remaining portion of the diameter after stopping, and the change in diameter during deceleration. These three signals are algebraically summed with a signal which is a function of the mandrel diameter, and when the summation is zero, slowdown is initiated.