In a single-signature duplicate document system, a secondary set of attributes is used in addition to a primary set of attributes so as to improve the precision of the system. In one embodiment, an anticorrosion substance is applied to a structural fastener. A plurality of intermediate transceiver units that are fewer in number than the number of end point encoder transmitter devices both receives and retransmits the high power FHSS signals. In an embodiment, communication of critical data between the master node and the member node may be encrypted with a session key. The vacuum part is disposed on an upper portion of the intake manifold such that noise from the engine may be decreased. An as-cast copper material is subjected to a multistage processing.