Because of the different types of phones that can be used there is a set tolerance on the modem of the Gate that has been turned down as low as can be set.  However, it may require some newer phones to press 9 many times in a row for the gate to open for the modem to pickup and open the Gate.  You will know that that the Modem has gotten your confirmation code when you hear a tone and the call is dropped.  This will let you know that the Gate Arm has lifted.