Bidirectional Retrieval of Magnetically Recorded Data

This document is a patent for a bidirectional data storage and retrieval system. It utilizes a mark track, in addition to standard data tracks, containing specialized binary control words. These control words identify 'blocks' and 'frames' of data on a movable medium like magnetic tape. The system uses complement obverse mark encoding, which ensures that control signals read in the forward direction are identical to those read in the reverse direction, thereby simplifying the logic required for bidirectional data access. The document includes technical diagrams of the recording format (mark and timing tracks), schematic diagrams of the decoding apparatus (shift registers and logic circuits), and charts detailing the mark word sequences used for operation.