isolator/circulator non-passband large signal behavior?

[CopperCone]

So Isolators are rated for some frequency range, so are circulators. What exactly happens if a signal is passed through beyond its range?

reflection? pass through? severe attenuation (thermal loss)? for passive types, with active types I can see them passing the signal through, as the op-amps begin to look like capacitors.

I can measure small signal behavior, but I am scared to do large signal tests.

I might make a transfer function, but I figured I would ask. I don't want to wreck expensive things if someone knows.