Marks and a method for multi-layer alignment. In one implementation, an encoderdecoder uses a parity check matrix having a size that corresponds to a length of information for each codeword. The terminal periodically transmits, to one of the base stations, information necessary for data transmission from a single base station out of the base stations. The detachable topsheet can be removed from the article and flushed in a toilet together with the human waste. A second region having a medium level of support is found in the front portion of the strap. This method utilizes only mechanical information to identify surge, as compared to present day antisurge controllers that use compressor thermodynamic information such as flow, pressure, and temperature to locate a compressor’s operating point on a compressor map compared to a surge region.