A system and method are disclosed for providing a network service. A suppression flag of the received alarm record is set in accordance with a result of the comparison. Each doored compartment also employs a lock and release assembly. The Viterbi decoder used for trellis decoding in a receiver can be designed to take advantage of knowledge concerning which different sets of symbols are precluded at prescribed times. This allows an increase in aspect ratio, hence improving efficiency at high loads.