How should the 986 alarm system work?

[Mikluuutus]

I have year 2000 Boxster S and it says it has option 534 - DIEBSTAHLSICHERUNG 433 MHZ (Theft security system 433 mhz)

So what the alarm system can do really? Does it have a motion sensor somewhere inside? What else?

Once went to the shop and my friend waited in the car. I used fob to lock the doors and still my buddy was inside the car. After a couple of minutes the alarm sound was on. I returned to the car and used fob. Alarm went off. Then went inside to the car with my friend and used fob to lock the doors again. We started moving inside the car but now no alarm sound went on no matter how hard we tried to move there. I also tried pull the door handle from inside but doors didn't open and no alarm went on. So now I'm very confused how does the alarm system works and would like to learn at least how it should work.

I'm asking this because I wan't to know can I trust to this alarm system or should I install a new one? Heading for road trip and don't want to get my car stolen or something stolen from inside the car.

[kjc2050]

I will assume you don't have an Owners Manual. If you do, suggest you read it. If not, refer to pp 22-23 in this pdf:

http://www.cannell.co.uk/Boxster_Manuals/986%20owners%20manual.pdf

[jcb986]

You should hear a ratcheting sound and then this, "You Are About To Be Exterminated You Scum Bag Thief". Better than the factory one.