I am going away for a few days, and the flat I am renting has a security door at the entrance to the building which opens with a plastic tag which one puts in front of the alloted place, and the it opens electronically. How would I get in and out on Shabbos, to go Daven, or is it better to stay in and Daven at home.
Answer:
An electronic key, such as the one you describe, may not be used on Shabbos (as ruled by contemporary poskim).
If you can come to an arrangement with a non-Jew, who will open the door for you on Shabbos, this will be ideal (although full amira le-akum is not permitted even from before Shabbos, in this case, which we can assume is a rabbinic prohibition, one can be lenient).
If there is no other way in or out, and no way of leaving the security door open, you should daven at home.
Although the use of electronic keys is becoming more and more ubiquitous, a halachic solution has not yet been found — though some are working on the idea.
Best wishes.
