An extendable and retractable eyewear telescoping retaining strap assembly consisting of an outer tubular strap member and an inner strap member slidably disposed within the tubular member. The converter utilizes circuitry that is not dependent upon the slew rate of an amplifier in recovering from the transition. While the bag supporting portions thus lifting the bag bundle, a new bag is fed into the space between the conveyance surface of the belt conveyor and the bag bundle. altering the model in dependence on that comparison by varying one or more of the said parameters.