I printed a custom DC to mail a book to my nephew. The input screen would not let me enter the last 4 digits of the zip, only the first 5. When the label printed, it printed junk numbers as the last 4. Is this imbedded in the barcode and will it mess up the book being delivered?

I've sent 5-digit custom DC and it hasn't been a problem.

Patty, did you just confuse 5-digit zip code in the msg above with 5-digit custom ISBNs?

Melanie, I would assume the barcode to be correct, I don't know why it would print gobble for the digits, but I'm assuming the barcode will be correct, since that comes from the database.

Melanie, it won't mess up the delivery of your nephew's book. If the barcode doesn't scan, we imput the numbers individually--all 16 or 22. Last resort is delivering without scanning.

When you enter an address at PBS, the system connects to the USPS web service that provides address standardization. The address you entered will get changed to the proper address that USPS expects, so if you put Seventh Avenue, but that town only has a Seventh Street, it will be changed to 7TH ST. The correct 9-digit ZIP code will also be added. So those extra four numbers you got in the ZIP code were most likely not junk, but just the result of the USPS address validation process.

Also, the 9-digit ZIP is not part of the barcode. Here's what's in the barcode:

420 + 5 digit ZIP + 91 + 01 or 02 for First Class or Media Mail + 9 digit PBS or Endicia ID + 8 digit Package ID + 1 digit Checksum

Cathy, thank you... That's fascinating to read!  It's nice to have the barcode deciphered. What is a "Checksum", however?

For more than you ever wanted to know about ISBNs and checksums (aka check digits), here is the Wikipedia entry for ISBN.

http://en.wikipedia.org/wiki/Isbn

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Oops!  The same principal applies to DCs.  Holiday stress made me forget we were in the Postal Regs discussion, hence the link about ISBNs.

A checksum is an extra digit that is calculated from the other digits in the number. It's there for verification purposes only, it doesn't add any new information.

When the barcode reader scans your DC barcode, the software inside it does a calculation using all the digits it read except the last one. It then checks to see if the calculated digit matches the last digit. If it does, then it can assume the barcode was read correctly. If it doesn't match, then it makes an "error" noise and the operator should try scanning the barcode again, or enter the number manually.