It should also be noted that the difference between the Vanguard and Sentinal is their limitations. The Vanguard will only go so far to the right and left (basically 90 degree's to the left, and the same to the right) where the Sentinel will go much further to the left and right (right around 270 I think it is, I don't have my manual with me, sorry), and the same holds true for the tilt, or up and down limitations. Only the Vanguard goes further than the Sentinel in this area, which to me is not a good thing and I feel that it should be corrected at the manufacturers level.
There is a post in one of the topics in the Forums here that make reference to getting past the limitations, but I very STRONGLY recommend that NO ONE makes any attemnpt at doing this per the given instructions. I have been inside these cameras, and not by choice, and I in no way recommend anyone attempt it unless you are a highly experienced technician. Things can very easlity go wrong. Wires can very easily come lose, screws are not easy to get out or back in, and having it all line up as it should when you reassemble, well, I'll just say, good luck! Thankfully, mine still works!