Bidirectional Retrieval of Magnetically Recorded Data

This patent describes a digital data storage system designed for bidirectional operation on a moving medium, such as magnetic tape. The system utilizes a unique "mark track" format containing "complement obverse" control words. By using this specific encoding, the system ensures that the signal generated by reading a control word in the forward direction is identical to the signal generated by reading its corresponding complement obverse word in the reverse direction.

Key aspects of the invention include:

• Mark Track Format: The medium is organized into blocks and frames. Control marks (such as block markers, guard frames, and tape end marks) are pre-recorded on a dedicated mark track to identify locations.
• Bidirectional Decoding: The apparatus employs a shift register and decoder that processes mark signals regardless of tape direction, simplifying the logic required for data retrieval and recording.
• Synchronized Timing: A timing track provides phased pulses to synchronize the operation of the tape controller and data transducers.
• Data Assembly: The system includes a sequence assembler that properly orders digital data depending on whether the tape is moving in the forward or reverse direction, allowing data processing equipment to interact with the medium efficiently in either mode.

This design facilitates rapid, accurate access to data storage spaces and reduces the complexity of circuitry needed for bidirectional data management.