Thanks, that is a very helpful link.  I didn't find that doing a search on the Hardi site.  Reading the material did lead to another question.  Can the job com be internal in the HC 5500 controller?  My HC5500 is version 4.0.  This was unclear to me in reading the tech bulletin.  If the job com control box must exist as a separate box, then I know that I don't have one.  I wish the tech bulletin had a pic of the job com other than the close up connections and I wish the layout for all connections were in the same diagram with the EZ 500 -- i.e. which ports would be used to connect to job com if the com1 port was connected to the EZ 500.

One more thought -- is the job com located with the cab controls or on the sprayer itself?