Vacuum Interrupter : A sealed "bottle" containing contacts of a switch inside a very high vacuum. When the contacts are parted in the vacuum, as there is no gas in the bottle to ionize, the current flow is quickly extinguished
Young & Company Electric Power Products and Related Engineering Services, Glossary of Electrical Terms, http://www.youngco.com/young2.asp?ID=4&Type=3, CA., USA 2001. (Electr Sfty - Amer) {514}