To be clear, it uses a similar mechanism to 2FA messages to place the call but there is only one authentication factor in this case.

My question is what kind of trouble can I cause by calling the inbound number from my call box? It picks up so presumably it is listening to something.

Also, how is the physical security of these devices? Are they managed from the keypad or is the control inside the building in a secure area? How does the FD get in?