# MERLIN BARCODE ERROR REFERENCE GUIDE

# February 4, 2002

## INTRODUCTION

This document describes the various error codes found in the MELRIN
Barcode Readability Report. Merlin is capable of evaluating post cards,
letters and flats. Even though the mail characteristics are different
from post card, letter and flats, the majority of the parameters of the
barcode are the same. This document provides the standards at which the
barcode printing must be set. (Per DMM)

The document makes references on the differences of the requirements
between letter and flats when it is appropriate. When no references are
made, the printing requirements are the same for all type of mail.

## METHODOLOGY

The MERLIN machine has three distinctive sections that help the mail
evaluation process. The first one is the singularizing process. This
process is achieved at the feeder section of the machine. The mail is
singularized by the suction cups and mechanically advanced to the input
rollers and delivered to the scale. The second process, settling, is
performed at the scale section. In addition to reading the weight of the
mail piece, the scale unit serves as the settling station for the mail
and as the input section to the imaging station. Third, as the mail
moves along to the stacker, the imaging station lifts an image that is
used for recognizing various evaluation parameters such as the barcode.
Lastly, the mail is stacked in the order it is presented at the feeder
section.

It is during the transport of the mail piece through the imaging section
that the barcode is recognized. The image is analyzed and barcode
recognition areas are defined. The best barcode recognition area is
defined out of all possible defined candidates. The one having the
highest barcode composition probability is selected and evaluated.

MERLIN utilizes two recognition engines for barcode analysis. One engine
does the reading of the barcode and the results are utilized for
sortation analysis. The second engine does the barcode quality analysis
within the specified tolerances. It is the results of the second engine
that are utilized in reporting of MERLIN Barcode Quality.

The barcode quality engine reports the barcode printing quality using a
set of error codes that are displayed with the image and summarized at
the bottom of the report. A sample of the MERLIN Barcode Analysis Report
is presented in the appendix.

**ERROR IDENTIFICATION**

Upper and lower case alpha characters are displayed below the bar when
errors/warnings are identified. Upper case characters represent hard
errors. One upper case character will fail a barcode. Lower case
characters represent warnings. A barcode with 10 or less warnings will
be accepted. 11 warnings for the same error code will fail a barcode.

## REPORTING ERRORS

![](media/image1.png){width="1.6666666666666667in"
height="0.7430555555555556in"}Bar is too tall

DMM Section C840 4.0 a, b

A full bar must not be greater than 0.135" in height.

A half bar must not be greater than 0.060" in height.

![](media/image2.png){width="2.65625in" height="2.182638888888889in"}

![](media/image3.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Bar is Too Short

DMM Section C840 4.0 a b

A full bar must be no less than 0.115" in height.

A half bar must be no less than 0.040" in height.

![](media/image4.png){width="2.6430555555555557in"
height="2.170138888888889in"}

![](media/image5.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Bar is Too Wide

DMM Section C840 4.0 c

No bar can be greater than 0.025" in width.

![](media/image6.png){width="2.6430555555555557in"
height="2.170138888888889in"}

![](media/image7.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Bar is Too Narrow

DMM Section C840 4.0 c

No bar can be less than 0.015" in width.

![](media/image8.png){width="2.6430555555555557in"
height="2.170138888888889in"}

![](media/image9.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Barcode Position Problem

See DMM Sections C840 2.3 - 2.5

![](media/image10.png){width="5.993055555555555in"
height="3.354861111111111in"}

![](media/image11.png){width="4.143055555555556in"
height="1.7902777777777779in"}

For letters the barcode position follows the two areas described in the
figure. For flat mail, the barcode can be within the flats OCR area
(Greater than 0.125 inches from each edge of the mail piece.) Also, the
barcode clearance zone requirements need to be observed within this
category.

![](media/image12.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

**Void (Area Without Ink)**

DMM Section C840 4.0

Extraneous ink or ink voids must not cause any bar to fail to meet the
minimum or maximum bar dimension standards.

![](media/image13.png){width="2.5833333333333335in"
height="1.4368055555555554in"}

![](media/image14.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Extraneous Ink Present

DMM Section C840 4.0

Extraneous ink or ink voids must not cause any bar to fail to meet the
minimum or maximum bar dimension standards.

![](media/image15.png){width="2.4194444444444443in"
height="0.7097222222222223in"}

![](media/image16.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Baseline Shift Problem

DMM Section C840 6.1

The individual bars of a barcode must not shift (be vertically offset)
more than

0.015 inch from the average baseline of the barcode.

![](media/image17.png){width="1.9569444444444444in"
height="0.9965277777777778in"}

![](media/image18.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Bar Tilt Problem

DMM Section C840 6.1

The combined effects of positional skew (slant or tilt of the entire
barcode baseline) and rotational skew (slant or tilt of the individual
barcode bars) must be limited to a maximum rotation of the bars of ±5
degrees from a perpendicular to the bottom edge of the piece.

For flat mailings, the requirement is limited to a maximum of ±10
degrees.

![](media/image19.png){width="2.703472222222222in"
height="1.1166666666666667in"}

![](media/image20.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Pattern Skew Problem

DMM Section C840 6.1

The combined effects of positional skew (slant or tilt of the entire
barcode baseline) and rotational skew (slant or tilt of the individual
barcode bars) must be limited to a maximum rotation of the bars of ±5
degrees from a perpendicular to the bottom edge of the piece.

For a flat mailing, there are no requirements at this time.

![](media/image21.png){width="2.609722222222222in"
height="1.0833333333333333in"}

![](media/image22.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Bar Pitch is Too Close

DMM Section C840 4.0 d

Measured over any 1/2 inch, horizontal spacing of the bars must be 22 ±2

bars per inch, and pitch (a bar and a space) must average at least
0.0416

inch but no more than 0.05 inch. The clear vertical space between bars
must

not be less than 0.012 inch or more than 0.04 inch.

![](media/image23.png){width="2.6430555555555557in"
height="2.170138888888889in"}

![](media/image24.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Bar Pitch is Too Far Apart

DMM Section C840 4.0 d

Measured over any 1/2 inch, horizontal spacing of the bars must be 22 ±2

bars per inch, and pitch (a bar and a space) must average at least
0.0416

inch but no more than 0.05 inch. The clear vertical space between bars
must

not be less than 0.012 inch or more than 0.04 inch.

![](media/image25.png){width="2.6430555555555557in"
height="2.170138888888889in"}

![](media/image26.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Background Reflectance is Low

DMM Section C840 5.1

A background reflectance of at least 50% in the red portion and 45% in
the green portion of the optical spectrum must be produced in the
following locations when measured with a USPS or USPS-licensed envelope
reflectance meter:

a.  The barcode clear zone of a card-size or a letter-size piece
    barcoded in the lower right corner.

b.  The area surrounding the barcode (within 1/8 inch of the leftmost
    and rightmost bars and 1/25 inch above and below the barcode) of a
    card-size, letter-size, or flat-size piece barcoded in the address
    block and of a flat-size piece barcoded elsewhere.

c.  The barcode clear zone on a non-barcoded card-size or letter-size
    piece in an upgradable mailing.

d.  

![](media/image27.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Print Reflectance difference is low

DMM Section C840 5.2

A print reflectance difference (PRD) of at least 30% in the red and
green portions of the optical spectrum is required between the
background material of the mailpiece and the barcode, when measured with
a USPS or USPS-licensed envelope reflectance meter. (PRD equals the
reflectance of the background minus the reflectance of the ink.)

![](media/image28.png){width="5.604166666666667in"
height="0.5208333333333334in"}

![](media/image29.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Barcode Clearance Problem

DMM Section C840 2.4c

C840.2.5 c,d,e

When the insert showing through the window is moved to any of its limits
inside the envelope, the entire barcode must remain within the barcode
clear zone, and a clear space must be maintained that is at least 1/8
inch between the barcode and the left and right edges of the window, at
least 1/25 inch between the barcode and the top edge of the window.

![](media/image30.png){width="3.3333333333333335in"
height="1.6666666666666667in"}

![](media/image31.png){width="3.3333333333333335in"
height="1.6666666666666667in"}

![](media/image32.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Connected Bars

DMM Section C840 4.0d

The clear vertical space between bars must not be less than 0.012 inch
or more than 0.04 inch.

![](media/image33.png){width="1.2861111111111112in"
height="0.6763888888888889in"}

![](media/image34.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Barcode Will Not Decode

DMM Section C840 1.0

When separated into groups of five, these bars sequentially represent
each of the digits of the ZIP Code (or ZIP+4 code or delivery point
code) for the delivery address, plus an additional digit designated as
the correction digit (check digit). The correction digit is derived from
adding the numbers in the ZIP Code (or ZIP+4 or delivery point code) and
determining which single-digit number must be added to that sum to make
the total a multiple of 10. The first and last bars of the barcode are
frame bars and they must always be full bars and be present.

![](media/image35.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Invalid Delivery Point Barcode

DMM Section C840 1.4

The correct DPBC must be derived as specified in Exhibit 1.4, which
provides rules for common and unusual address formats. This code may
also appear in conditions in which a digit is printed incorrectly or the
check digit is incorrect.

![](media/image36.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Bar space is too close

DMM Section C840 4.0 d.

Measured over any 1/2 inch, horizontal spacing of the bars must be 22 ±2
bars per inch, and pitch (a bar and a space) must average at least
0.0416 inch but no more than 0.05 inch. The clear vertical space between
bars must not be less than 0.012 inch or more than 0.04 inch.

![](media/image37.png){width="2.6430555555555557in"
height="2.170138888888889in"}

![](media/image38.png){width="1.6666666666666667in"
height="0.7430555555555556in"}

## Bar space is too far apart

DMM Section C840 4.0 d

Measured over any 1/2 inch, horizontal spacing of the bars must be 22 ±2
bars per inch, and pitch (a bar and a space) must average at least
0.0416 inch but no more than 0.05 inch. The clear vertical space between
bars must not be less than 0.012 inch or more than 0.04 inch.

![](media/image39.png){width="2.6430555555555557in"
height="2.170138888888889in"}

In addition to the error codes, there are other messages that the MERLIN
barcode evaluation process reports and they are as follows:

## BARCODE NOT FOUND

This condition is present when neither the barcode analysis engine nor
the barcode reader engine produces a favorable read. Causes for this
error condition are:

-   Erroneous check digit

-   Incorrect barcode symbology (incorrect POSTNET representation-tall
    and short bar combination)

-   More than 62 bars present

-   Frame bars not present

-   Improper bar height. When tall bars are extremely short or when
    short bars are extremely tall.

-   Improper barcode clearance. When text or any other printing is in
    contact with the barcode.

-   Any other printing parameter selected that renders the barcode
    unrecognizable.

## DECODED-NO IMAGE

In this error condition, MERLIN knows that there is a barcode but the
barcode analysis engine does not have an image available for performing
the barcode analysis. The reader engine was able to recognize it. This
error condition is associated with poor printing of a barcode for the
analysis engine to recognize it and perform measurements.

## NO IMAGE FOUND

This error condition is reported if barcode readability failed, but due
to internal MERLIN file transfer, an image was unable to be included in
the report. Readability errors are included in the legend.