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Bar Code Record Format

IP.com Disclosure Number: IPCOM000053122D
Original Publication Date: 1981-Sep-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Bobart, KL: AUTHOR [+4]

Abstract

Each line of a bar code record is comprised of control codes prior to and subsequent to message-content codes. The coding technique is every transition a bit (ETAB), and vital control codes which may appear in the same area are selected in patterns which generally are not confused by normal machine malfunction.

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Bar Code Record Format

Each line of a bar code record is comprised of control codes prior to and subsequent to message-content codes. The coding technique is every transition a bit (ETAB), and vital control codes which may appear in the same area are selected in patterns which generally are not confused by normal machine malfunction.

The first field of bar code observed in the normal reading of the message is termed a header field and contains four sub-fields. The first sub-field read is termed the guard pattern. It is formed by one wide black bar followed by one wide white bar, and it is used to allow the bar code signal processing system to become initialized by reference to a known pattern so that it will more accurately determine the location of bar edges.

The next sub-field in the header is the sync pattern, which is a narrow black bar followed by a narrow white bar followed by a narrow black bar, and finally followed by a narrow white bar. Such a regular, repetitive pattern has a very high probability of being recognized correctly. The processing system, upon recognition of the sync pattern, ignores prior extraneous marks and determines initial decoding parameters.

The next sub-field in the header is the start control code, which is a six bit pattern. The start control code defines the content of the message which follows. A start logical record (SLR) code signifies that the message which follows is the first of one or more messages which are deemed related. A start physical record (SPR) code signifies that the message which follows is one after the first of such related messages.

The last sub-field in the header is the parity bar. It is a single, narrow black bar provided to give the entire header a predetermined bit count equal to that of the last four sub-fields of the trailer. When the line is read in reverse direction, the equal number of bits simplifies decoding by the same algorithms.

ETAB bar code, used in this system, is taught in an article entitled "ETAB Bar Code" by D. W. Phillips and R. C. Ross appearing in IBM Technical Disclosure Bulletin 21, 2883-2884 (December 1978). As there fully described, each transition from white to black defines the start of a bit, the end of which being defined by the next transition from white to black. Any transition from black to white also defines the start of a bit, and the end of that bit is defined by the next transition from black to white. Bits of predetermined, intermediate length are deemed to have the significance of 1, while bits of predetermined shorter or longer length are deemed t~ have the significance of 0. The header field just described requires 13 bars.

The message field follows immediately after the header field on the same line. The length of this field is controlled by the bar code density and by the width of the paper on which the code is printed.

The trailer field follows on the same line immediate...