A storage and retrieval system includes a continuous track and a plurality of individual storage units stacked in multiple columns or rows. After entering the shell, some gas travels upward, which reduces the volume of gas traveling downward toward an oil sump. Inserting a segment sync signal and a field sync signal into the trellis-encoded packet, and a vestigial side band modulation and an RF conversion of the packet are performed to transmit the VSB-modulated and RF-converted packet. A portion of the second face folds back on itself allowing a portion of the first face to meet at least a portion of the second face in opposing engagement. In response to the users’ selection of a particular link enhancement, then that link enhancement function would be performed without requiring the any further action. The units have a variable assembly with regard to the longitudinal direction of the retainer rail.