Unexplained button?

Hi all. Just bought a 2008 2nd gen Prius to use for work. It needs a bit of tidying up. I found a button which is between the smart entry and start system button and the tyre pressure reset button. Although my car doesn’t have these, there is a button that sits between these. It’s a picture of a car with what looks like interior motion coming down from the roof? Sorry don’t know how to explain. It also has ‘off’ written on it.

I have attached a photo of the button. I have checked the manual and there is no mention of this. The diagram at the beginning of the manual shows the two switches either side but shows blank for this.

I wonder if anyone knows what this button does, I assume it’s something to do with the alarm.

Thanks in advance.