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Data Recording and Transmission: Part 19 - Cyclic Redundancy ChecksMay 5th 2020 - 09:30 AM

The CRC (cyclic redundancy check) was primarily an error detector, but it did allow some early error correction systems to be implemented.

There are many different CRCs but they all work in much the same way, which is that the data to be protected are divided by the CRC polynomial. This was done serially by shifting the data bits into the CRC generator at the same time as they were being written to a medium such as disk or tape or sent into a serial transmission line.

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Data Recording and Transmission: Part 18 - Modulo CountingApril 6th 2020 - 09:00 AM

The mathematics of finite fields and sequences seems to be a long way from everyday life, but it happens in the background every time we use a computer and without it, an explanation of modern error correction cannot be given.

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Data Recording and Transmission: Part 17 - Error Correction IIMarch 5th 2020 - 09:00 AM

Here we look at one of the first practical error-correcting codes to find wide usage. Richard Hamming worked with early computers and became frustrated when errors made them crash. The rest is history.

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Data Recording and Transmission: Part 16 - Error CorrectionFebruary 3rd 2020 - 09:00 AM

Error correction is fascinating not least because it involves concepts that are not much used elsewhere, along with some idiomatic terminology that needs careful definition.

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Data Recording and Transmission: Part 15 - Error Handling IIJanuary 2nd 2020 - 09:00 AM

Errors are handled in real channels by a combination of techniques and it is the overall result that matters. This means that different media and channels can have completely different approaches to the problem, yet still deliver reliable data.

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Data Recording and Transmission: Part 14 - Error HandlingNovember 29th 2019 - 09:00 AM

In the data recording or transmission fields, any time a recovered bit is not the same as what was supplied to the channel, there has been an error. Different types of data have different tolerances to error. Any time the error rate is in excess of the tolerance, we need to do something. Error handling is a broad term that includes everything to do with errors. It includes studying the error sensitivity of different types of data, measures to prevent or reduce errors, measures to actually correct them and measures to conceal the error if correction is not available or not possible.

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Data Recording and Transmission: Part 13 - Electronic MemoryOctober 22nd 2019 - 09:00 AM

Having looked at magnetic and optical storage media, John Watkinson turns to electronic memory with the emphasis on flash.

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Data Recording and Transmission: Part 12 - The Optical Drive - PlaybackAugust 20th 2019 - 09:00 AM

Optical disks rely totally on the ability of the pickup to follow and focus on the data track. It is taken for granted that these mechanisms are phenomenally accurate, work at high speed despite being made at low cost and need no maintenance.

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