Abstract: A side cab providing enclosed pedestrian entrance to, or egress from, an airplane access door. The side pivot cab facilitates engaging one end of an access passageway with an aircraft access door by aligning interface structure for engagement with the aircraft. A side pivot cab rotates about an axis near, or associated with, a wall of an access passageway from an airport terminal building. A single adjustable wall extends or contracts to accommodate rotation of a pivot cab. Rotation capability of a side pivot cab may approach 270 degrees.

Abstract: A method and apparatus for positioning and tracking a Random Access Memory (RAM) optical head over an information storage media having a plurality of tracks formed by optically readable deformations ("pits") in the media including, a central controller, a laser diode optical-system carrying head which is movable transversely of the tracks in incremental steps for coarse positioning of the head over a selected band of tracks and a servomechanism which positions the laser's objective lens over a specifically addressed track and maintains it there until another track is addressed. Also discussed is a unique method of generating a tracking error signal as an input to the servomechanism which includes the asynchronous detection of a sector mark and the generation of an independent clocking signal from the synchronous detection of off-track pairs of pits spaced uniformly between other data in the track to produce the tracking error signal.