I was asked to recommend a scanner by a customer who sent me samples of their bar codes. They were all Interleaved 2 of 5 code, which is a numeric only code whose only saving grace is that you can print a lot of digits in a small space. Here are three symbologies encoding the numbers 1 to 8:
You can see that Interleaved 2 of 5 takes up the least space, but Code 128 is pretty close. Interleaved 2 of 5 has a built in defect in that the stop/stop patterns are not unique and if the scanner enters or leaves the code in a spot that resembles a start or stop, the code can be short scanned.
Code 128 is always printed with a check digit anyway and has a unique start/stop pattern, making it a superior code to I 2 of 5.
My customer’s bar code looked like this:
This is a picture from our microscope. Notice that the narrow bar measures .1 mm, or 3 mils. This is a 300 dpi printer. The wide to narrow ration of this code should be 3 to 1; this is printed at 4 to 1. Lastly, the narrow bar under the red arrow should be one element wide, this one is two.
Their printer is doing a bad job printing this code, but fortunately for them modern scanners are pretty forgiving and this code can be read reliably with a Xenon with high density optics.