alarm system

my stealth has an alpine alarm system i noticed in it, did they come standard in the car's or would some one have put it in themselves? i am trying to figure out how to get it to work and have gotten nowhere. i took the middle counsel out of the car and noticed another smaller alpine box with a red light and a sensitivity gauge it looks to be, it looks like there was something to turn the guage like a key or knob of some sort and it is missing. is there something missing or not

i dont know about the alpine, but on my viper there is a sensitivity guage and there is a screw that u can turn to make it more or less sensitive, so ur probably missing that screw