Smartkeys have both RF and IR capability. The RF signal can lock, unlock, or open the trunk. The panic alarm can also be activated via RF.

The IR function of the key is different. In addition to locking and unlocking, the convenience feature can be used in IR mode. If you look at the exterior handles on your front doors you'll see a small "window". If the key is aimed at one of these windows, and the unlock button is pressed and held, the car will unlock and the windows and sunroof will open. The reverse will occur if the locking button is pressed and held. For this feature to work though, you'll need to be within a few feet of the car. This is a nice feature to have during the warmer months. In fact, it's now known as "summer opening".

The other IR function takes place when the key is inserted into the ignition switch. The rolling codes programmed into the key are read by EIS via IR. This is how the Drive Authorization System determines the correct key is being used. The key is powered inductively by EIS, so if the key batteries are dead the car can still be started. I hope this answers your question.