[asterisk-users] Long call setup times on SIP to zaptel calls

[Luki]

Jordan said "the SIP device sends the request almost instantly" so
it's not the SIP phone's fault. The channel bank probably takes 1-2
seconds to pick up and wait/check for dial tone, 1-2 second dialing,
and the telco takes 1-2 second to ring. So the complete PDD is ~5
seconds.

You could try putting a Ringing(); before the dial statement to let
the SIP phone know the call is being connected. I believe once
progress comes from the Dial command, it will replace the Ringing.
However, if your channel bank answers the call right away, this won't
help.

--Luki