> "tip" trouble has been fixed too. The origin is modem's CD signal. 
> "tip" require that is always on, isn't it.

That depends. You can set the serial port to be in "local" mode, wherein
it doesn't wait for a carrier before connecting. To set this mode,
type "stty /dev/tty00 clocal". man stty will tell you many of the
options for stty.

Take care,

Bill