private void btnAccess_Click(object sender, EventArgs e)
        {
            bool?useExtended = null;

            if (chkUseExtendedTime.CheckState == CheckState.Checked)
            {
                useExtended = true;
            }
            else if (chkUseExtendedTime.CheckState == CheckState.Unchecked)
            {
                useExtended = false;
            }

            SafeInvoke(
                () => DoorControlClient.AccessDoor(_door.token,
                                                   useExtended,
                                                   tbAccessTime.Text,
                                                   tbOpenTooLong.Text,
                                                   tbPreAlarm.Text, new AccessDoorExtension()));
        }