Abstract: There is disclosed a conveyor system having a frame and an endless chain slidably mounted on and coiled about the frame and driven by a chain drive motor and wherein an endless belt is coursed about the frame for bearing edgewise about a predetermined length of the chain to effect circulation of the endless belt and wherein a tension drive motor removes the endless belt slack from the frame to effect such edgewise bearing and wherein the speed of the tension drive motor is continuously monitored and adjusted to maintain at a predetermined belt tension by controlling the distance between a dancer roller to a drive roller driven by the tension drive motor as measured by signals from an ultrasonic sensor representative of a predetermined target distance or differential distances between such ultrasonic sensor and the target associated with the dancer roller.