Fail safe redundant power supply in a multi-node computer system

A data processing system and method providing a jumper which provides standby power from a redundant power supply to one of at least two critical functions in a frame having bays for holding at least two nodes. The redundant power supply supplying power to one of the nodes in the frame and one of the critical functions. A jumper is slidably engageable in the frame in place of one of the nodes. The jumper, when engaged in the frame, transfers power from the redundant power supply to the other of the critical functions. The jumper is included in a jumper book of an airblock which includes passive airblock books. Mechanical keys on the passive airblock books prevent the removal of the jumper book until after the passive airblock books are removed.