Abstract: A mercury tilt switch having a hollow metal housing with opposite open ends. An insulating glass member is disposed at, makes a glass-to-metal compression seal with, and closes, one of the open housing ends. A metal end cap is disposed at, resistance welded to, and sealably closes, the other of the open housing ends. The housing has an outer wall portion defining a single chamber therewithin which extends between the insulating glass member at the one housing end and the metal end cap at the other housing end. At least one electrical electrode is sealably mounted through the insulating glass member and projects from opposite sides thereof to the outside of and into the housing chamber. A quantity of mercury is disposed in the single housing chamber and is flowable between and contactable with the electrode at the one housing end and the metal end cap at the other housing end upon tilting and countertilting of the housing.