I've found this
article which gives some insight in the difference between the old and new Apple remote (especially the table near the end).
Appearently the new center button sends the same command as the Play/Pause button but with a prefix that is added (only) when the button is pressed.
Holding the button will only repeat the actual command, not the prefix.
The prefix is different for the center and the Play/Pause button and allows to distinguish between both buttons for receivers that are aware of that.
At the same time compatibility with older receivers that are not aware of this is kept.
What I'd like to know now is:
1. Can this behavior (i.e. sending a prefix when a button is pressed and repeating only the actual command code) be achieved using my TSU3000 Pronto (not the freshest model, I admit).
2. What are the prefix codes for the Center and the P/P buttons?