What does this section mean?

What does the pulse-shaped signal mean in the fourth section of this PI controller? There's no such information in the block parameter setting...

Answer 1

[Aquatris]

Probably the integral reset functionality. So when you disable and enable the controller, the integral term will reset to 0 to prevent any unwanted behaviour.

If you go inside the block, you will probably see that signal is attached to a external reset input of an integrator

Edit: Here is the link to documentation where they explain the reset input.