Better be quick on the trigger. Those shore to ship missiles that line the Persian Gulf have a flight time to target of less than 30 seconds. Those young sailors in the Gulf are at grave risk if somehow the crazy mullahs start shooting.
This would be purely retaliation. Mess with our forces, your lights go out permanently. Or at least long enough for your government to collapse.
With the weapons they are talking about, if real, would just do their stuff and what the Iranians would know is that there was yet another incursion into their air space then suddenly no one could talk to each other and nothing worked. I think this not the sort of EMP that requires a detectable explosion.