Abstract: A mercury activated float switch comprises a base member, a resilient fulcrum, desirably comprising an aperture in a resilient sheet, supported on said base member and at least two flexible electrical current carrying conductors supported for pivotal movement about the resilient fulcrum. A float member has associated therewith a switch assembly in which the electrical conductors terminate as spaced apart contacts. An angled mercury-containing race within the float member communicates with the switch assembly. As the liquid level changes, the float member pivots about the resilient fulcrum between first and second positions. The mercury in the race occupies the end of the race remote from the switch assembly when the float member is in its first position and flows into the switch assembly to bridge the space between the contacts when the float member is in its second position.