To get firing solution you need bearing and range two points in time. Then you just need some simple geometry and maths to get AOB and speed.
Normally you get all of this with the periscope.
With the IXX you get bearing with the hydrophones and range with the active sonar.
The only disadvantage is that you need to do it at least twice and it takes practice to get good situational awareness just through sound.
__________________
|