A Cross Reference table. The table maintains an index of an object which is also the table index, and a counter that indicates how many times this object was referenced. When using this table for more than one referenced table, which uses the same range of indexes, then the index should be shifted by a unique offset per table. In ACE2002 this table is used for TD and for FR Desc. Thus, the index for FR Descriptor is: FR Descriptor index + offset. The offset is described in the ACE2002 NMS SRS.