A movable barrier operator (10) can have at least two automatic modes of operation. These modes of operation can differ from one another at least with respect to their respective utilized maximum-applied-force thresholds, such that one of the modes of operation correlates to a reduced maximum-applied-force threshold. Selection between these available maximum-applied-force thresholds can be based, at least in part, upon whether an obstacle detector is operably coupled to the movable barrier operator. In one embodiment, a primary controller (30) and a secondary controller (31) can be utilized to effect the controlled selection and usage of the available maximum-applied-force thresholds. In another embodiment, maximum permitted speed of travel for the movable barrier can also be determined, at least in part, as a function of whether an obstacle detector is available to the movable barrier operator.