NOVELTY - The switch has a snap-dome (50) supported at its intermediate position (52) on a circuit board (3). The snap-dome has electrical contacts (53,57) and an actuator portion (56) outboard and inboard of the intermediate position, respectively. An actuator (15) displaces the actuator portion to flatten the snap-dome such that the snap-dome transitions between a convex-outward configuration in which the contacts electrically contact electrical connectors (54,55) and a concave-outward configuration in which the contacts space from the electrical connectors.    USE - Pressure-sensing switch for over-pressure condition sensing such as in gas generator cartridge or reactor module.    ADVANTAGE - By deploying and inverting the snap-dome from the convex-outward configuration to the concave-outward configuration, the pump can be switched off in simple, efficient manner. The snap dome offers a non-linear characteristic with a negative portion of the force-displacement characteristic which is beneficial for providing switching hysteresis and thus preventing rapid uncontrolled toggling close to the switching threshold. The use of a support under the dome to allow the dome to break contact with the substrate makes the system fail-safe in event of debris contamination of contacts. The switch is made softer and sensitive to pressure, making the switch easily tuned for actuation to a third configuration within a tight pressure window.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a method of operating a pressure-sensing switch having a substrate and a dome member supported on a substrate at an intermediate position of a dome member and having a first electrical contact portion outboard of an intermediate position and an actuation portion inboard of an intermediate position; and    (2) a method of operating a fuel supply cartridge.    DESCRIPTION OF DRAWING(S) - The drawing shows the cross-sectional side views of a pressure sensing switch in three different configurations during operation.    Circuit board (3)    Actuator (15)    Snap-dome (50)    Intermediate position (52)    Electrical contacts (53,57)    Electrical connectors (54,55)    Actuator portion (56)