Talk:Barcode reader

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This page still kinda stinks (needs improvement). Sorry I removed so much stuff, but it is better to say nothing at all than to spread egregiously wrong information. I don't have the time right now to fix it.

Contents 1 Level of accuracy on barcode scanners 2 Unanswered questions 3 "SYMBOLOGIES" isn't a real term 4 Barcoding in stock system 5 Reading by yourself

[edit] Level of accuracy on barcode scanners

I would like to know how often a normal barcode scanner makes a mistake? The level of accuracy depends on the symbology and quality of the barcode and the decode algorithm that the barcode scanner uses. Most Symbologies have a check digit or checksum that validates the characters in the barcode using a calculation defined in the standard, but there are some like interleaved 2 of 5 that don't that means the scanner cannot perform this check. No check digit is the most common cause of missreads. Barcodes can be checked for quality using a barcode verifier and are graded on the ANSI standard A-F (F for fail). Most scanners will be 99.99% accurate on grade C and above codes with a check digit. The decode algorithms can sometimes contain flaws that allow a miss read.

I would also like to know how much information (in bytes) can be stored in a barcode

Note also that bluetooth readers are available now also, and USB readers are no longer rare.

There should probably be a link to a barcode page for this information rather than here, because the error prevention/detection is much more a function of the symbology and the print quality than the reader itself.

[edit] Unanswered questions

This article doesn't really explain how exactly does a barcode reader read the codes in a barcode. For example, when a user is swiping a handheld barcode reader across a barcode, how exactly is the variations in light reflected back synchronized to the physical width of a bar or white space? If a user's hand does not sweep over the barcode in an absolutely constant speed, wouldn't the data become garbled? If his swiping speed was half while swiping a 1-width bar, it would be decoded as a 2-width bar. If his swiping speed was doubled while sweeping a 2-width bar, the bar would be decoded as a 1-width bar. What is the missing piece of technology that makes barcode readers work? Does anyone know? 193.251.135.123 12:03, 22 August 2005 (UTC)

They have to assume that the swipe speed is constant, at least over some small distance. This distance is not necessarily the entire bar code, however; the symbology can be designed to make it possible for the reader to resynchronize itself over shorter distances. The problem is similar to that of transmitting serial data over a single wire, with no clock reference (as does a Serdes). 66.30.14.1 06:56, 21 March 2006 (UTC)

in CCD barcode scanners, the device just "takes a picture". In a laser scanner, the speed at which the laser swipes across the barcode depends on the frequency of the oscillating mirror. So a 1-width bar could give the same response as a 2-width bar at a different distance. However, the barcoding software could be looking at the relative widths of the bars, i.e. whether its a long or short bar. At the near range the device stops reading when the angle subtended by the barcode becomes close to the scanning angle of the laser. At the far working range, the failure to read a barcode is due to factors such as noise, the modulation of the signal, as well as the larger size of the laser spot. The increased frequency of the input signal could also be a factor. --Nathaniel 13:26, 23 March 2006 (UTC)

[edit] "SYMBOLOGIES" isn't a real term

Just a note on the section labelled 'symbologies.' Symbology is a fictional field. You can even do a search on SYMBOLOGY and find this out. The nearest thing to 'symbology' would be symbolism, I think. But the word 'symbolism' doesn't seem to fit the subject matter.

Lamont McCroskey

A "symbology" is a noun. Symbologies are specifications for how to encode data into barcodes. It's a real word that you can find on many barcode-related sites. Jehochman 04:20, 18 January 2006 (UTC)

[edit] Barcoding in stock system

Please can someone advise how a barcoding system can be used within the workplace for stock inventory. Would you scan the barcode and that would then enter the data onto a computer system for reviewal if needed?

[edit] Reading by yourself

Is there a way to read bar codes by yourself?