Locking a 2007 Prius

Picked up my 2007 Prius two weeks ago - so far, it's great.

Got a question if someone knows about these things. I've contacted my dealer three times alreaady. They promised to respond, but no answer yet (wait till they want me to respond to their evaluation card).

Anyway, it concerns locking the vechicle. The book isn't very clear. Also, the dealer told me they installed an theft alarm system to the car (something they do for all vechicles on their lot). They placed a small red pushbutton switch on the panel just forward of the parking brake, said it was to program the theft alarm. I know I've pushed it several times while installing my XM radio, and can't get the dealer to tell me what the consequences are of pushing it.

Using the door button or key fob, I get a low inside beep and parking lights flash when I press it. Ok, the book is correct here.

However, when I press the power door lock switch on the drivers side inside door, I get three low horn beeps before I close the door, and then three LOUD horn beeps when the door is closed. This usually brings looks my way from others nearby !

My question is - what's arming the theft alarm system? The outside button, the key fob, the inside power lock - any or all or none ? Also is there any way to disable those loud horn beeps ?

Anyone got any ideas about this ?

thanks..