Sector-based structures can contain lists of track parameters, vector hit parameters, or crate structures. The sector data structure consist of a sector header followed by zero or more data items. The sector header is two words per crate and contains the following information.
A sector of data can come from one or more crates of electronics. The header is identical to the header in the crate data structure that follows, but the data contained within it is partitioned into several blocks that begin with their data size in words.