Abstract: A coupler for coupling an accessory to a dipper arm and a control system for such a coupler. The invention concerns a quick hitch coupler for coupling an accessory to a dipper arm of a back actor such as may be used by an earth working apparatus. The quick hitch coupler comprises a body member adapted for coupling to the dipper arm, a fixed engaging means mounted on the body member for engaging a first one of a pair of coupling pins mounted on the accessory, and a moveable engaging means mounted on the body member for engaging a second one of the pair of coupling pins of the accessory. The invention also relates to a control system for controlling the release of an accessory from any quick hitch coupler coupling the accessory to a hydraulically operable arm of a machine, operated by a pressurized hydraulic system.