A foldable mattress includes plunger matrix sections and corresponding flexible connectors connecting the plunger matrix sections in side-by-side relation. Preferably, the gravel guard is connected to the exterior surface of the leg-covering member and below the interior connection between the foot-covering member and the leg-covering member to provide a substantially watertight connection between the foot-covering member and the leg-covering member. Simultaneously, CRC is computed on each received N-bit of the data frame and an FCS register is updated. If no pertinent rule is found, then a pertinent rule is retrieved from a source external to the firewall, and loaded at the firewall. Circuitry in the transponder is electrically connected to the loop and arranged to become inoperative and disable the transponder if the loop is broken. Moreover, the processing module selects some of the plurality of temporary images according to the analysis results to integrate images.