A fluid filter system including a filter housing having an inlet chamber that surrounds the inner chamber that houses the filter cartridges. The method comprises the operation of verifying and validating the detection of the disengagement of the previously engaged gear by detecting the angular velocity of the primary shaft corresponding to the gear to be disengaged, and comparing the detected value of said angular velocity with at least one reference angular velocity. Based on these answers, topics of interests are identified. If a MDC assigned to a mobile station does not satisfy a predetermined radio communication quality, other MDCs for lower priority application are freed and reassigned to the mobile station. The microprocessor is configured to perform a LADAR image analysis that compares the three-dimensional image data with the protected area boundary and fixed object definitions to identify one or more potential intruders. The floor elements are provided with a male vertical assembly joining member on a third edge while a fourth, opposite, edge is provided with female vertical assembly joining member.