I had occasion to help set up a new Google Voice account and noticed that Google Talk was not available as a destination by default, so I did the usual trick of switching over to Gmail to place one call from the web interface. But because it was a new account, it started out with Hangouts enabled and not Google Voice, and no phone icon was shown! However there is a dropdown menu in the lower part of the left hand column, which in this case was slow to appear (Google was having some server issues), but once it showed up I could go into that menu and there was an option to revert back to using Google Talk. Once I did that, the page refreshed and the phone icon appeared, and then I could make the one call from the browser that sets up Google Talk as a destination in Google Voice.
This implies that if Google ever stops offering the option to revert to Google Talk rather than using Hangouts, it might not be possible to get a new Google Voice account and use it with an Obihai device, because it won't be possible to enable Google Talk as a destination.
Let's hope that doesn't happen anytime soon!
