DeltaFix
From Signal Identification Wiki
DeltaFix was a DGPS system that was used to provide precision positioning used in the survey and oceanographic industry.
DeltaFix, owned by Fugro Survey, was a development of HyperFix that enables DGPS (Differential GPS) corrections to be transmitted using the data time slot 'D' in HyperFix transmissions.
There are currently no DeltaFix stations operating in Europe anymore.