Is there some system that transmits information to your door card reader on what the new key is, or is it something different entirely?
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Hotel receptionist here (Even now I’m at work)
It’s not very ELI5 but I don’t know how to simplify it.
All doors have a battery-operated microchip that has its own “name” (namely room number)
A room card is basically a really dumbed down contactless debit card on its inside. We program in the room number and checkout date on a programmer so your card stops working after your stay (so you couldn’t freeload). The microchip is more or less smaller programmer on read-only. When you put your card near the door, it reads if the card is for its room and if the date is valid. If everything is in order, it opens the door.
Now, say you lost your door card. We make you a new one. How does it know if the old ones are obsolete and shouldn’t open the door to them?
Technician told me every card has ID and you disable the old ones by telling the microchip with the new card “HEY, I’m the new card, old one is made obsolete, they overrode it sooo don’t let it in”.
TL;DR The new door card tells the door to not let the old card in.
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