A disposable tourniquet and its method of use is disclosed. A control module is mounted to the bottle bottom and defines an interior area. A second hollow cylinder is provided with the discharge needle and rotatably disposed inside the first hollow cylinder. A second transistor connects the first transistor to a reference voltage during the read operation. A diagnostics unit generates summary information by compressing the operation data and comparatively decides whether the summary information matches the other summary information of the other processing unit every control cycle.