From the North Sea ATC side, different areas of the NS are given different rig freqs. Some end up being traffic areas (Piper, Beryl). I thought that all the rigs in the area used that freq to talk to the decks.
In the ESB there are a few deck freqs, 2 of which are also ATC freqs. This is due to change as the ESB is going to get bigger so to overlap the Sumburgh SSR, and go down to just 122.25. This was all supposed to happen last month, and may well happen in the next few. Don't know about the deck freqs though.
[This message has been edited by Concrete (edited 05 January 2001).]