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Disclosed is a code to be implemented in an 18-track magnetic tape. This code has 4 tracks carrying redundancy (the first two and the last two) while the central tracks carry the information (as in ).
English (United States)
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Code for Multitrack Error-Correction in Magnetic Tapes
Disclosed is a code to be implemented in an 18-track
magnetic tape. This code has 4 tracks carrying redundancy (the first
two and the last two) while the central tracks carry the information
(as in ).
The code has the following error-correcting capability: two tracks in error, one
track in error together with two erased tracks or four erased tracks. It turns out
that this performance is optimal  and improves the performance of the code
described in , which can only achieve this correction power in particular cases.
The idea of the new construction is similar to . In this
case, the cross-parity lines run across all the tracks. The four
parity lines are as follows:
1. A vertical parity line. 2. A diagonal parity line
with slope 1. 3. A diagonal parity line with slope
-1. 4. A diagonal parity line with slope 1/2 (or
An easy description of the four lines is as a combination of a rook, two
bishops and a knight.
Encoding and decoding procedures are fairly simple and similar to the ones
The code can be extended to families with greater error-correcting capability
by taking more lines with different slopes.
1 A. M. Patel, "Adaptive Cross Parity (AXP) Code for the
IBM Magnetic Tape Subsystem," IBM Journal of Research
and Development, 29, 6, 546-562 (November 1985).
2 P. Piret and T. Krol, "MDS Convolutional Codes," IEEE
Trans. on Information Theory, IT-29, 2, 224-233 (March