Right - 10 codes vary from place to place - and even in the same place (for instance, NYPD 10 codes are different than NYPD Transit Division 10 codes!)
That is why the National Incident Management System (NIMS) - which is a superset of the "Incident Command System" (ICS) REQUIRES the use of "plain speach" - no 10 codes - you get to the site, you say "I'm on site"
BTW EVERYONE (partiularly the folks here) should probably take the FEMA "IS-& A Citizen's Guide to Disaster Assistance" at
http://training.fema.gov/EMIWeb/IS/is7.aspAnd if you want to learn more about how FEMA is SUPPOSED to work, take IS-22, IS-100 (a big one) IS-200 (ICS for single resources), IS-271 was fairly good, IS-288 is good if you do any volunteer work, 292 wasn't bad
Haven't take 394 (That'slooks new since the last time I looked) - IS-700 was very good
If you look at the list, you'll see a LARGE stack of classes you can take. When I have "down time", I'll often take one, just to keep the skill level up (and yeah - I'm just a dumb civilian...)