I am thinking of extending this configuration a little further. I want to be able to FAX reliably. As I understand it, the Obi does not support T.38 while Callcentric does. To enable FAXing on Callcentric, I would need some other ATA which supports T.38. Fortunately, I happen to have a spare Linksys SPA2102 around.
So here is what I am considering for my set-up:
SP1 - GV (my regular GV account for voice calls)
SP2 - GV (a GV account for FAXing only using G.711)
Line - My SPA2102 set up with Callcentric
On my FAX-only GV account, I would forward all calls to my IPKall number (rather than Google Chat) which would be bound to CC so that incoming FAXes would come in thought the Line port using the SPA2102. Presumably, incoming FAXes would be free, as the GV telephone number is free, the IPKall telephone number is free, and incoming CC calls are free.
To send a FAX, I would:
1) Try to use GV on SP2 and hope that G.711 is reliable enough to get the FAX through.
2) But if the FAX were really important, I would dial **8 followed by the actual FAX destination telephone number to send the FAX via the SPA2102 using Callcentric with T.38.
Would this arrangement work? Even though the Obi does not support T.38, can a FAX machine hooked up to the Obi Phone port pass through the Line port to the SPA2102 in order to send a FAX using T.38?
If possible, I would like to get incoming FAXes for free, and also to send FAXes for free if I can (using GV) but at low cost if necessary (using CC).