I worked as a mobile electronics installation technician for 2 years to put myself through college. I have used the merc switches that are on your link, martlet and I have never had any issues with them not functioning properly as long as the wiring is secured properly. What they are is a small glass tube with a tiny amount of mercury inside of it encased within a larger bubble of plastic to keep it safe from breakage. Sandman, you are right as far as the FDA ban... they stopped us from using them about 12 months ago due to the harmful nature of mercury. The new ones use a ball bearing that rolls in a tube to make the connection.
