Pressure responsive electrical switch apparatus for monitoring the pressure level in an enclosed chamber comprising a header and first and second generally elongated terminals, each terminal having a longitudinal axis, the header mounting the terminals electrically isolated from each other and from the header, the second terminal having a distal free end extending laterally generally 90.degree. from the longitudinal axis of the second terminal,
- a movable contact arm assembly having a generally U-shaped base composed of electrically insulative material comprising first and second legs extending downwardly from a bight portion, an electrically conductive member having a first portion with a first end formed with first and second legs extending from a central portion, the first and second legs of the electrically conductive member encased in respective first and second legs of the U-shaped base, the central portion extending between the first and second legs of the U-shaped base and being electrically connected to the first terminal, the electrically conductive member having a second portion with a second end formed with a movable contact received under and biased toward the distal free end of the second terminal, the electrically conductive member having an intermediate portion supported by and extending from the bight portion of the base, and
- a pressure sensor assembly comprising an open ended sleeve extending upwardly from the header, a pressure reference chamber having an open end, a pressure responsive disc movable between first and second oppositely dished configurations closing the open end of the pressure reference chamber and received in the open ended sleeve, the sleeve being formed by a wall having a vent opening therethrough,
- the disc being adapted to transfer motion to the intermediate portion of the electrically conductive member when moving from one of the configurations to the other configuration to move the movable contact away from the distal free end of the second terminal.