Values 0xA, 0xC, 0xE (aka ":" "")are noted as "Control characters" in ABA/ISO 7811 spec for track three data. What does this actually mean? Does anyone have any examples of how they are used? I understand how stop, start and separator are used on a magstripe card but not control characters.
I would like to use the values 0xA, C, and E, as well as 0xD (separator value - "=") as meaningful digits in a proprietary encoding scheme (in order to cram more application usable data on the track). Are there any possible drawbacks to this? For instance, it's not a good idea to use
0xF (stop sentinel - "?") in such a manner as I've seen encoders which (correctly so) would interpret this as the end of your data and not encode any digits sent after that. Likewise the start sentinel; so my scheme will have the start and stop sentinels in the right place. However, it seems harmless to scatter these other 4 characters throughout my stripe in ways that are meaningful to my application. But before I commit to that, I would like to make sure there are no problems with using these values in such a manner. Examples of problems would be that certain encoders wouldn't play well with this usage, or certain card encoding software packages would not play well with this usage.Thanks!
Dave