DECtape Patent 3387293

This patent describes a system for bidirectional retrieval of digitally recorded data from a moving storage medium, such as magnetic tape.

The core innovation lies in the use of dedicated "mark tracks" alongside standard information tracks. These mark tracks store binary-coded "mark words" that define and identify data storage "blocks" and "frames" on the medium.

A key feature is that control words located at the beginning of a block in one direction are designed to be the "complement obverse" of those at the end of the same block when read in the opposite direction. This ensures that the same logical signal is produced by the decoding apparatus regardless of the medium's direction of movement (forward or reverse).

This bidirectional compatibility provides equal facility for data identification and retrieval in either direction, leading to rapid, flexible, accurate, and reliable access to stored data. The system also utilizes a timing track for synchronization, and a decoding apparatus that processes mark signals to generate control signals for data transfer. This approach simplifies logic circuits, programming, and increases data handling speed and operating accuracy.