Editing PostBar

{{Disputed|date=November 2024}}
'''PostBar''', also known as '''CPC 4-State''', is the black-ink [[barcode system]] used by [[Canada Post]] in its automated [[mail]] sorting and delivery operations.  It is similar to other 4 State barcode systems used by [[Australia Post]] and the United Kingdom's [[Royal Mail]] (from which it derives), but uses an obscured structure and encoding system unique to Canada Post.  This particular bar code system is used on "flats" (which are larger-than-letter-size pieces of mail, such as magazines) and parcels.

[[Image:CPC PostBar legend.svg|right|]]
This [[symbology]], derived from the [[RM4SCC]] system used by the British Royal Mail, uses a series of bars, each of which can individually have one of four possible states, to encode information used in automated sortation and delivery onto each piece of mail.  Each bar can either be short and centred (known as a ''tracker''), medium and elevated (an ''ascender''), medium and lowered (a ''descender''), or full height.  This symbology also uses an element known as a ''[[Data Content Identifier]]'' (or DCI), which specifies what types of information are encoded into each barcode, such as postal codes, customer information, and exact delivery points.  The information that goes into each barcode is obtained from the address printed on the front of the envelope it is ultimately printed on, as well as the physical dimensions of each piece of mail.  This code also uses a [[Reed–Solomon error correction]] technique, so that in case a particular piece of mail is mishandled, the information encoded in the barcode can still be correctly decoded.

==Character sets==
[[Image:CPC PostBar character chart.png|right|300px|thumb|Chart of PostBar characters]]
Four character sets are used in PostBar codes, known as "A", "N", "Z" and "B" characters.  Three-bar A characters are used exclusively to encode letters, and two-bar N characters encode only digits.  Three-bar Z characters can encode either letters or digits.  A and N characters are typically used to encode [[Canadian postal code|postal code]]s and [[country code]]s.  Z characters are used for address locators, product types, and customer and service information.  B characters are one bar each, and are used to encode base-4 machine IDs for Canada Post's internal uses.

The bars making up a character can be interpreted as base-3 digits.  A full height bar encodes 0, a short lower bar (an ascender) encodes 1, and a short upper bar (a descender) encodes 2.  The leftmost bar in a group is the most significant [[ternary numeral system|trit]], and may have the value 3, with both upper and lower bars short (a tracker).

In other words, short upper and lower bars are assigned weights of 18 & 9, 6 & 3, and 2 & 1, from left to right.  Since the first bar has 4 possible values, and the following bars have 3, 2 bars can encode 4×3&nbsp;= 12 values, while 3 bars can encode 4×3×3&nbsp;= 36.

N characters are simply encoded as the values 0–9.  Only the value 9 requires a leading 3.

Z characters use the full 36 combinations representable by 3 bars.  The values 0–25 encode the letters A–Z, and 26–35 encode the digits 0–9.

A characters have a somewhat peculiar encoding.  They can also be decoded as three base-3 digits (a leading 3 is never used), with the values 2–26 mostly encoding A–Y.  Exceptions are that 0 encodes M, 1 encodes H, 9 encodes Z (rather than H), and code 14 is not used (rather than encoding M).
<!-- Presumably this has something to do with the two urban postal codes of Toronto (M) and Monteral (H). -->

==PostBar formats==
Canada Post uses nine different formats of PostBar codes&mdash;three "domestic" barcodes, used on mail within [[Canada]], two "global" codes, used to route mail outside Canada, three "service" codes, used on customer-applied barcodes, and an "internal" code, used for testing, maintenance, and tracking purposes by Canada Post.

Each barcode begins and ends with an identical pair of bars, known as "start" and "stop" fields.  These are made up of one ascender and one tracker.  The Data Content Identifier is always the first character after the start field.

Placeholders used to detail each PostBar format below are A, N, Z and B for the character sets described above, * for the start and stop fields, # for a space character (two full-height bars followed by one tracker), and [RS-''nn''] for the error-correction field, where ''nn'' is the number of bars used.  Bold Z's indicate DCIs.

===Domestic===
DCI's used in domestic barcodes fall within the range of A–L.
*PostBar.D07: * '''Z''' ANANAN [RS-12] *
*PostBar.D12: * '''Z''' ANANAN ZZZZ # [RS-12] *
*PostBar.D22: * '''Z''' ANANAN ZZZZZZZZZZZ [RS-12] *

===Global===
DCI's used in global barcodes fall within the range of 1–9.
*PostBar.G12: * '''Z''' NNN ZZZZZZZZ [RS-12] *
*PostBar.G22: * '''Z''' NNN ZZZZZZZZ ZZZZZZZZZZ [RS-12] *

===Service===
DCI's used in service barcodes fall within the range of M–U.
*PostBar.S06: * '''Z''' ZZZZZ [RS-12] *
*PostBar.S11: * '''Z''' ZZZZZZZZZZ [RS-12] *
*PostBar.S21: * '''Z''' Z ZZZZZZZZZZZZZZZZZZZ [RS-12] *

===Internal use===
DCI's used in internal barcodes fall within the range of V–Z.
*PostBar.C10: * '''Z''' ANANAN [RS-30] BBBB *

===Business reply mail===
52 bar long 4-state barcodes are used by Canada Post for business reply mail (BRM) addressing and payment.<ref>{{cite web|title=Designing Business Reply Mail|url=https://www.canadapost.ca/tools/pg/3_Designing/PSbrm-e.pdf|publisher=Canada Post|accessdate=18 February 2016|date=11 Jan 2016}}</ref> As of 2013 or earlier the previous BRM barcode, which were [[Code 93]]-type barcodes, were deemed non-machineable.<ref>{{cite web|title=Machineable Standard (S/L) Business Reply Mail|url=https://www.canadapost.ca/cpo/mc/assets/pdf/rates/2013_machineable_standard_brm_ef.pdf|publisher=Canada Post|accessdate=18 February 2016}}</ref>
An extended 73 bar long BRM barcode '' 'C73' '', scheduled for availability from 2011, was indefinitely postponed.<ref>{{cite web|title=Business Reply Mail Changes FAQ|url=https://www.canadapost.ca/cpo/mc/business/productsservices/marketing/brm/faq.jsf#B8|publisher=Canada Post|accessdate=18 February 2016}}</ref>

==See also==
*[[RM4SCC]] – The barcode used by [[Royal Mail]]
*[[Intelligent Mail barcode]] - The barcode used by the U.S. Postal Service
*[[POSTNET]] - The barcode used by the U.S. Postal Service until 2011

==References==
{{reflist}}
Related websites
*U.S. Patent 5,602,382 – {{cite web|url=http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5602382.PN.&OS=PN|title=Mail piece bar code having a data content identifier|date=February 11, 1997|accessdate=2007-01-06}} – Assigned to Canada Post Corporation
*{{cite web|title=4-State Bar Code Handbook|url=http://www.canadapost.ca/common/offerings/address_management/pdf/dbc_handbook-e.pdf|publisher=Canada Post Corporation|accessdate=17 February 2016|archiveurl=https://web.archive.org/web/20060321110734/http://www.canadapost.ca/common/offerings/address_management/pdf/dbc_handbook-e.pdf|archivedate=21 March 2006|location=Ottawa}}
*[http://auspost.com.au/media/documents/a-guide-to-printing-the-4state-barcode-v31-mar2012.pdf "A Guide to Printing the 4-State Barcode" from Australia Post (PDF, 645,947 bytes)]

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{{Barcodes}}

[[Category:Barcodes]]
[[Category:Canada Post]]