For all normal system activations, the real-time game is put on hold:
To activate a system...announce "STOP" and raise a fist. All other players stop what they are doing and listen.
This seems important for multiple reasons, including making sure the game is in a single consistent state during the resolution of the activation.
However, the rules also seem to treat triggering a mine differently from activating a system:
At any time, except while surfaced, the Captain can trigger a mine by raising a fist, announcing "TRIGGERING A MINE"
So: does triggering a mine count as a system activation?
If yes, does that mean that you have to charge the system once to drop and then charge it again to trigger, and that the engineer must have weapons systems online for both drop and trigger? Or if no, does that mean that the game isn't on hold while the trigger is resolved, even though the game is on hold while the very similar torpedo explosion is resolved?