You can use an UC520 that does everything and not even expensive on the refurbished market.
Not expensive, but not even cheap. By the way, seams to be a great product and, of course, should be easier to set up than the pbx. Thank you Paolo
I know this topic is (now) 4 years old, but I have not been able to locate any place that shows what is IMHO one reason for this problem.
When you do a factory reset on these phones (79xx), only the firmware is left there.
It tries to get its load from a tftp server, and it seems that the tftp client does something wierd, and is not able to download the files from *many* tftp servers included the embedded tftp server of IOS (routers), and the CUCM tftp service. Even my standard 3cd tftp server rejects the second file request with "malformed option".
Just using a more lenient tftp server does the trick. I was not able to spot what the problem is with the requests but it could just be that the transfer ID is the same for all file requests?
Whatever, just try a different tftp server and you may be fine. I used linux's tftp-hpa-0.40.
If someone wants to dig into the reason, attached there's a capture of "rejected" requests of a "bricked" 7911G.