What is the deal with the cabin safe?
This safe is each cabin is basically a standard hotel room safe. It operates by swiping a plastic card (with a magnetic strip on back) in the diagonal slot you see on the door of the safe. That will cause the door to lock. Later on, you would then swipe the exact same card again in that slot. That would cause the door to unlock, opening the safe. You have about a shoebox amount of volume in the safe to store your valuables.
You can use almost any plastic card with a magnetic strip on back(credit card, driver's license,ATMcard, gift card, etc.). You could even use your Sail&Sign card, but they warn you not to use it. They say that it will damage the magnetic information on the strip rendering it useless (NOT TRUE, I learned first hand). Rumor has it the main reason not to use your Sail&Sign card to lock your safe is that it would make the safe vulnerable to a dishonest cabin steward who could use their master Sail&Sign card to gain acess to the safe. I don't know how true that rumor is.
They use this master Sail&Sign card on the job to open every stateroom door, in order to clean the rooms.
Anyway, I found that cards with wider magnetic strips on back work better with the safe. I first used my Kinko's Photocopy card on the safe (it has a narrow magnetic strip on back).I kept getting a "Card Read Error" message unless I swiped the card just right. I then used my Florida's Drivers License (which has a wide magnetic strip on the back). My Driver's License worked every time with no problems.
I had no problems with the safe during my cruise, and the valuable contents inside remained safe. Even when I naively used my Sail&Sign Card to lock the safe (before reading the warning not to do so). I also used the room safes on the two other Carnival ships I was on in past cruises, all with no problem as well.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013