Method and apparatus for striping spare storage in a data storage system. The method includes activating, if a receiver associated with the RTD does not respond to the packet-based call within a predetermined time period, an answering-and-recording function associated with the RMMS to enable the ARF to receive and record packets pertaining to the packet-based call while permitting the receiver to continue to hear the caller. A transmission rate of the first layer decreases substantially linearly from a center toward a periphery of the optical filter, and the transmission rate distribution is symmetric with respect to the center. The methods enable the fabrication of the connectors, with exemplary fabrication methods including spin forming and radial expansion. According to the present invention, even if unnecessary contact between battery blocks occurs in a power supply unit, a short circuit or the like does not occur.