A pressure responsive electrical switch uses precalibrated snap acting monometallic or bimetallic discs freely disposed in a disc seat formed on a base member. Over pressure protection in the form of a surface spaced just beyond the normal snapped position may be provided to avoid calibration changes. A flexible thin gasket is positioned over the disc and is sealed to the base by trapping between the base and a cap which is clamped to the base. Several seal variations are shown to provide varying degrees and types of seals. A rocker member having a specially curved surface rests on a movable contact arm and transfers motion from the disc to the movable arm. A support for the movable arm has a portion which is formed with a complementary curved portion which cooperates with the rocker member and a stationary contact to limit the amount of stress imparted to the movable contact arm. Several different embodiments of precalibrated disc switches are shown including a differential pressure switch and a switch in which the disc is part of the electrical circuit.