Keycard lock

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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 common types of keycards in use, including the mechanical holecard, barcode, 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.[1]


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.

Newer keycard systems use radio-frequency identification (RFID) technology such as the TLJ infinity.[citation needed]


Mechanical keycard locks employ detainers which must be arranged in pre-selected positions by the key before the bolt will move. 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 approximately 4.3 billion 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.[2]

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.[3]

Some models of card locks found in hotels use batteries. When the batteries fail the lock will fail safe, meaning that the lock stays open and therefore the door can be opened without the keycard. It is also possible to design the lock to fail secure, causing the door to stay locked when power is lost.


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 their 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. Offices have also slowly installed digital locks that integrates with key cards and biometric technology.[4] For example, KISI is a new technology that integrates keycard into smartphone to allow office users and guests to open their doors with smartphone. 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.


Illustrations of Authentication Access Control & Keycard Technology
A hotel entry card and used as a light switch 
Illustrated instructions for use of mag stripe key card 
Electronic Lock with Keycard System, ANSI 
Access control utilizing magnetic strip technology 


  1. ^ "Key Card Inserted In Slot Opens Gate At Automated Parking Lot." Popular Science, August 1954, p. 94, mid page.
  2. ^ "US patent 4,149,394: Lock arrangement employing mechanically acting code card and key card". Google Patents. IFI CLAIMS Patent Services. April 17, 1979. 
  3. ^ "Key Card Comparisson and information."
  4. ^ Widness, Brett. "Bringing Keycard Technology To Smartphones". Urban Land Institute. Urban Land Institute. Retrieved 10 June 2015.