A backplane is a circuit board, which connects several connectors in parallel to each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. It is used as a backbone to connect several printed circuit board cards together to make up a complete computer system. Backplanes are normally used in preference to cables because of their greater reliability. In a cabled system, the cables need to be flexed every time that a card is added to or removed from the system; and this flexing eventually causes mechanical failures. A backplane does not suffer from this problem, so its service life is limited only by the longevity of its connectors.

Backup seals are used in conjunction with O-rings for both static and dynamic sealing applications. These seals prevent extrusion of the o-ring or seal when it is subjected to high pressure, and/or larger extrusion gaps. The back-up seals should be used on the opposite pressure side of the seal.

Backup Steering Systems provides hydraulic pump, an accumulator, a mode control valve, a main solenoid valve, and a pair of back-up solenoid valves. The hydraulic pump and the accumulator are both connected to a main hydraulic line. The mode control valve is set in fluid communication with the mode control valve and the main solenoid valve. When the main solenoid valve is actuated the pump is in fluid communication with both service brakes to operator induced braking.

The back-up wrench comprises a stationary jaw having an angular gripping wall adapted to grip two adjacent sides of different size connectors, and a rotatable jaw having a concave wall adapted to grip limited portions of two symmetrically-opposite sides of the connectors. The rotatable jaw is pivotally mounted on a cylindrical bearing surface provided by a forward extension of a plate whose rearward end is pivotally mounted on a stationary handle forming integral part with the stationary jaw. A rotatable handle is pivotally coupled to the plate. Conventional means are provided in and between the handles for applying and releasing the gripping action of the jaws against the four sides of the connector.