Magnetic Cards for Hotel Doors

Taken from Zomet Institute
The Zomet Institute is an Israeli high-tech non-profit organization specializing in IT equipment and electronic appliances designed to meet Halacha.

Question: I was asked by a couple who will be flying to Prague next week how to open the door of their hotel room on Shabbat. The doors have no physical keys and can only be opened with magnetic cards. Inserting the card into the proper slot opens the lock and turns on electrical appliances in the room (such as lights, air conditioning, etc.). My question is: Can the mechanism be neutralized by blocking some eyehole with masking tape?

Answer: I do not know of any simple technical solution to this problem, except for sealing the doorjamb open with tape. But then the door remains unlocked for the entire time (it is very important to place all the valuables in a safe before Shabbat).
 
This leaves a problem of service people and maids who might discover the tape and lock the door. It is thus necessary to leave a request at the desk or to hang a “Do Not Disturb” sign on the door of the room.
 
Because of the dire need and for reasons of “human dignity,” some rabbis allow asking a Gentile to open the door (similar to what is often done with elevators, which is problematic in itself, but I will not elaborate here). This is in spite of the fact that it is almost impossible to do this without making an explicit request to the Gentile. I did this once on a trip abroad. It takes into account the fact that electrical activity is only forbidden by a rabbinical decree, so that it involves asking a Gentile to violate a rabbinical decree in a case of great need and in order to maintain “human dignity.”
 
However, if inserting the card also turns on the lights in the room, its use is a direct Torah violation. In this case, a second magnetic card (which can usually be obtained from the desk) should be left in the proper slot inside the room, so that the lights will remain on all the time. Another possibility is to leave the light on only in the bathroom or at the entrance of the room.