anchor.diff:      {noreply, State};
   
   handle_info(Info, State) ->
  -    Callback = erlang:get(?CALLBACK),
  +    Callback = callback(),
       Callback:handle_info(Info, State).
   
   %% @private
  
positive.code: 
  %% Internal functions
  
  
negative.code: 
  -spec send_response(#sip_request{}, #sip_response{}) -> ok | {error, Reason :: term()}.
  send_response(Request, Response) ->
      Callback = callback(),
      sip_ua_server:send_response(Request, Response, Callback).
  
  %%-----------------------------------------------------------------
  