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A keycard lock is a lock operated by a keycard, a flat, rectangular plastic card with identical dimensions to that of a credit card or American and EU driver's license which stores a physical or digital signature which the door mechanism accepts before disengaging the lock.
There are several popular type of keycards in use including the mechanical holecard, bar code, magnetic stripe, Wiegand wire embedded cards, smart card (embedded with a read/write electronic microchip), and RFID proximity cards.
Keycards are frequently used in hotels as an alternative to mechanical keys.
The first commercial use of key cards was at automated parking lots to raise and lower the gate where users paid a monthly fee.
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 mag stripe card, or in the case of RFID cards, merely being brought into close proximity to a sensor. Keycards may also serve as ID cards.
Many electronic access control locks use a Wiegand interface to connect the card swipe mechanism to the rest of the electronic entry system.
Mechanical keycard locks employ detainers which must be arranged in pre-selected positions by the key before the bolt will move. This principle was the base for the first known mechanical holecard operated lock, the VingCard, invented by Tor Sørnes. This was a mechanical type of lock operated by a plastic key card with a pattern of holes. There were 32 positions for possible hole locations, giving up to different keys. The key could easily be changed for each new guest by inserting a new key template in the lock that matched the new key.
In the early 1980s the key card lock was electrified with LEDs that detected the holes.
Magnetic strip (sometimes "stripe") based keycard locks function by running the magnetic strip over a sensor that reads the contents of the strip. The strip's contents are compared to those either stored locally in the lock or those of a central system. Some centralized systems operate using hardwired connections to central controllers while others use various frequencies of radio waves to communicate with the central controllers. Some have the feature of a mechanical (traditional key) bypass in case of loss of power.
Some models of card locks used in hotels use batteries and when the batteries fail the lock will fail safe meaning the lock stays open and therefore the door can be opened without the keycard. It may be possible to set this to fail secure meaning when the power is out the lock stays locked.
Computerized authentication systems, such as key cards, raise privacy concerns, since they enable computer surveillance of each entry. Currently RFID cards and key fobs are becoming more and more popular due to its ease of use. Many modern households have installed digital locks that make use of key cards, in combination with biometric fingerprint and keypad PIN options.
Bar code technology is not a secure form of a key, as the bar code can be copied in a photocopier and often read by the optical reader.
- "Key Card Inserted In Slot Opens Gate At Automated Parking Lot." Popular Science, August 1954, p. 94, mid page.
- US patent 4,149,394