Article 4473 of comp.misc:
From: balcer@gypsy.siemens-rtl (Marc J Balcer)
Subject: Re: U.S. Postal Service Zip+4 bar code:  what is it?
Summary: Summary of Responses and Other Information
Message-ID: <3767@siemens.UUCP>
Date: 16 Nov 88 18:47:18 GMT
Organization: Siemens RTL, Princeton NJ

Thanks for all the replies to my question about USPS bar codes.  
Here's a summary, as well as other information I researched myself.

The code itself is a 2-of-5 code, with leading and trailing "1" bars
and a checksum digit.

The five binary digits represent 7, 4, 2, 1, 0.
Each decimal digit in the zip code is represented by the following pattern:
    0 = ||...	    5 = .|.|.
    1 = ...||	    6 = .||..	    . represents a short bar
    2 = ..|.|	    7 = |...|	    | represents a long bar
    3 = ..||.	    8 = |..|.
    4 = .|..|	    9 = |.|..

Either a 5-digit or 9-digit (Zip+4) code may be encoded using this
method.  The actual bar code contains either 6 or 10 digits.  The
last digit is selected such that the sum of all of the digits
(including the last one) is a multiple of 10.

For example, the zip code for Siemens is 08540:

    1.	The check digit is 3.  (0 + 8 + 5 + 4 + 0 + 3 = 20)

    2.	The bar code is

	|||...|..|..|.|..|..|||.....||.|

        |0----8----5----4----0----3----|

According to the USPS Domestic Mail Manual (Section 917.528), the bar
code is placed at the bottom of the envelope so that the first bar is
between 3.875 and 4 inches from the right edge of the envelope.  The
baseline of the bar code must be 0.25 inches from the bottom of the
envelope.

A "1" bar must be 0.125 inch (plus or minus .010 inch) high.
A "0" bar must be 0.050 inch (plus or minus .010 inch) high.
All bars must be 0.020 inch (plus or minus .005 inch) wide.
Bars should have a nominal horizontal spacing of 21 to the inch, 
plus or minus one bar.

The USPS does give bulk-rate discounts for presorted and bar-coded mail.  
The best discounts are for Zip+4 presorted and bar-coded.  

Check with your local postmaster before sending your own bar-coded
mail.
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Marc J. Balcer
[balcer@gypsy.siemens.com]
Siemens Research Center, 755 College Road East, Princeton, NJ 08540
(609) 734-6531
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