Hi Lazzman, is this a 123 chassis Mercedes? You mentioned a 300SD in your other post.
Ok, it was rare to see factory installed alarm systems on a 123 chassis. The alarm module on that car should be located under the driver's side dash. I've attached a diagram from the parts catalog, it's #592 in the picture. I would expect the module to be made by Becker, there should be some labels on it. You should be able to simply disconnect the module. Let me know what you find.