As you may know, I'm a big fan of Freephoneline (FPL). One of the nice things is the great support provided in the online communities:
Over the years, I've received a lot of great help from members of the community; I've learned a lot about FPL, VoIP in general, ideal network conditions and design to best run this stuff...best of all, how to keep it up and running, and what to do when something goes wrong!
In some small way, I've tried to help and hope I have helped other users. For my own setup, I use the Grandstream HT-701 ATA (analog telephone adapter), which last I checked is the adapter that Fongo provides for their monthly phone service. While many FPL users have moved on to Obihai ATAs, there are others who still use different options from Cisco, Linksys, and Grandstream. The last available configuration guide was for an earlier firmware, so I wanted to put together something more current to help others, even if it's just a few people.
You can access the PDF here: http://forum.fongo.com/viewtopic.php?f=15&t=18839. If I have any updates to it, such as troubleshooting tips, I'll be sure to add them there.
Thanks, and hope this helps! And thanks to everyone in the two FPL communities that helped me navigate these tricky waters.