RB570 is an 18Volt replacement transformer that is used with most GTO/Mighty Mule UL series automatic gate openers * Maintains battery backup by providing a trickle charge of power to the gate opener battery through the control board * Transformer should never be connected directly to any battery * NOT compatible with any pre-UL gate opener models, including the FM250. Please call GTO at 1-800-543-4283 with questions about compatibility