Topic summary
Keycard
Extracted from the Wikipedia article Keycard lock.
Overview
Keycard systems operate by physically moving detainers in the locking mechanism with the insertion of the card, by shining LEDs through a pattern of holes in the card and detecting the result, by swiping or inserting a magnetic stripe card, or in the case of RFID or NFC cards, merely being brought into close proximity to a sensor. Keycards may also serve as ID cards, or as part of an NFC system, have the code transmitted to a mobile phone to be placed into a digital wallet system such as Apple Wallet or Google Wallet, negating the need for a physical keycard.