Abstract: A pressure-operated safety switch is applied to a point in the compressed air system, which requires monitoring for presence of pressurized air. Pressurized air is introduced into the switch through a tube or other suitable fitting at the point needing monitoring. The pressurized air is split internally to force redundant, independent pistons to an extended position. Under safe conditions (i.e., the absence of pressurized air), electrical contacts on each piston makes physical contact with switch body contacts to create two independent electrical switch paths. Pressure required to force the pistons away from the electrical contacts is adjustable by using a spring and set screw, for example.