This field specified the new Phase IV synonym for the node.  Phase IV
 synonyms can be used in place of fully specified node names, particularly
 with applications that do not support full node names.

 The synonym must be from 1 to 6 letters (A to Z) or digits (0 to 9),
 with at least one letter.

 This is initially filled in with the current synonym value, but can be
 changed to a new synonym, or left blank to indicate no synonym.