They are not onboard but loaded from the web data base. Harmony has a great database including all the X10 codes for the IR543. You do not need to learn them.

The large database of the Logitech web-based remote setup is one of its big pluses. Unfortunately they also force you to update to their latest application code every time you visit that site and do any kind of change to your setup. This really stinks!

Good luck,