Extended Channel Interpretation (ECI) is an extension to the

communication protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics (computer scien ...

that is used to transmit data from a bar code reader to a host when a

bar code A barcode or bar code is a method of representing data in a visual, Machine-readable data, machine-readable form. Initially, barcodes represented data by varying the widths, spacings and sizes of parallel lines. These barcodes, now commonly refe ...

symbol is scanned. It enables the

application software Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a c ...

to receive additional information about the intended interpretation of the message contained within the barcode symbol and even details about the scan itself. ECI was developed as a

symbology A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conce ...

-independent extension of the Global Label Identifier (GLI) system used in the

PDF417 PDF417 is a stacked linear barcode format used in a variety of applications such as transport, identification cards, and inventory management. "PDF" stands for Portable Data File. The "417" signifies that each pattern in the code consists of 4 ...

bar code.

Description

In the default mode, where Extended Channel Interpretation is not in effect, the interface between the reader and the host is said to be in "Basic Channel Mode". In this mode, each octet of transmitted data is defined (by the corresponding bar code symbology standard) to correspond directly to a single data character

code point In character encoding terminology, a code point, codepoint or code position is a numerical value that maps to a specific character. Code points usually represent a single grapheme—usually a letter, digit, punctuation mark, or whitespace—but ...

in some default character set, normally

ISO/IEC 8859-1 ISO/IEC 8859-1:1998, ''Information technology — 8-bit single-byte coded graphic character sets — Part 1: Latin alphabet No. 1'', is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in ...

(Latin-1). However, when ECI is in effect, the data interface is said to be in "Extended Channel Mode". In this mode the interpretation of the transmitted data is defined by the current ECI modes that are enabled, which are activated and deactivated by "ECI indicators" included in the transmitted data. Within the data transmission protocol the use of ECI is indicated explicitly by a modification to the symbology indicator that the decoder will recognize and interpret accordingly in order to disambiguate between ECI and non-ECI encoded messages. If the reader is not ECI enabled or the application does not support the ECI indicators that are in effect then the scan should be aborted. The ECI information is not part of the ultimate bar code message and its use is normally transparent to the user in basic image scanning scenarios. The application presents the user with the intended message, but it does not normally render the various ECI indicators that were used to derive this message or to provide annotation or additional metadata. For advanced applications (including system debugging and data validation) the ECI information may be rendered inline with the bar code message or extracted and presented separately.

Types of ECI indicator

ECI indicators may be included at various points in the transmitted message, and may be either of "encodable" type or of "non-encodable" or "signal" type. ; Encodable ECIs : These indicators are part of the message and define the format for all or part of the data, such as the intended character set or the data compression scheme that is in effect such as

Gzip gzip is a file format and a software application used for file compression and decompression. The program was created by Jean-loup Gailly and Mark Adler as a free software replacement for the compress program used in early Unix systems, and in ...

. ; Signal ECIs : These indicators are not part of the message and they may either be embedded in the bar code symbol ''separately from the message'' or may not be present in the symbol at all but added by the reader at scan time. Signal ECIs are used to convey information about the processing of the data, such as whether it is a fragment of a multi-symbol scan process, whether an error condition occurred during reading, or even to provide environment information such as what ambient light level was measured or provide a low-battery indication.

Common use case: Enable support for international character sets

The most common use for Extended Channel Interpretation is to allow usually unsupported national character sets such as

Arabic Arabic (, ' ; , ' or ) is a Semitic languages, Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C ...

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

, or

Japanese Japanese may refer to: * Something from or related to Japan, an island country in East Asia * Japanese language, spoken mainly in Japan * Japanese people, the ethnic group that identifies with Japan through ancestry or culture ** Japanese diaspor ...

to be used reliably in bar code symbols. An ECI-enabled bar code symbol may use several character sets by embedding several character set ECI indicators to delimit segments of the message that are encoded using different code pages. For most barcode symbologies, the default code page (if not specified by ECI) is

(also known as

Latin-1 ISO/IEC 8859-1:1998, ''Information technology — 8-bit single-byte coded graphic character sets — Part 1: Latin alphabet No. 1'', is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1 ...

) as shown in bold below. Well-known ECI values, which are commonly used to indicate that a message segment is encoded using a specific

code page In computing, a code page is a character encoding and as such it is a specific association of a set of printable characters and control characters with unique numbers. Typically each number represents the binary value in a single byte. (In some co ...

character encoding Character encoding is the process of assigning numbers to Graphics, graphical character (computing), characters, especially the written characters of Language, human language, allowing them to be Data storage, stored, Data communication, transmi ...

: Available ECI codes from Symbology.dev
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References

External links

AIM ITS/04-001 International Technical Standard: Extended Channel Interpretations
{{webarchive , url=https://web.archive.org/web/20120427015909/http://www.aimglobal.org/standards/symbinfo/tsc-04-002%20eci%20pubrev.pdf, date=April 27, 2012 Data interchange standards Character encoding