Thanks for the advice.
I would like all the orbiters (set up as ext 200, 201, 202, 203) and the new SIP phone (204) to all ring so in FreePBX I set up a ring group called 'all' and listed all the ext's.
Then in the 'Inbound routes' page, at the very bottom in the 'Set Destination' section, I clicked on 'Ring groups' (which only appears when you have added one) and then 'All' (for the group I had set up earlier).
Seems to work now.
The phone was a bargain at $43!!