The issue is initial call setup for PSTN access.  The control for that is not exposed via gtalk, only through the gmail client.

On Mon, Aug 30, 2010 at 11:34 PM, jesse <chat2jesse@gmail.com> wrote:
what is the point use to gMail? The backend of Gmail dialing is
actually Google Voice.

FS can integrate with Google Voice via some java library to make
outgoing calls for U.S and Canada..

jesse


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-Rupa