interface to connect the card swipe mechanism to the rest of the electronic entry system. Magnetic stripe Magnetic stripe (sometimes "strip") based keycard locks function by running the magnetic stripe over a sensor that reads the contents of the stripe. The stripe'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. Passive RFID RFID cards contain a small chip and induction loop which the transmitter on the keycard reader can access. The main advantages with RFID cards is that they do not need to be removed from the wallet or pass holder - as the keycard reader can usually read them from a few inches away. Access control In the case of the hotel room lock, there is no central system; the keycard and the lock function in the same tradition as a standard key and lock. However, if the card readers communicate with a central system, it is the system that unlocks the door, not the card reader alone. This allows for more control over the locks; for example, a specific card may only work on certain days of the week or time of day. Which locks can be opened by a card can be changed at any time. Logs are often kept of which cards unlocked doors at what times. Privacy Computerized authentication systems, such as key cards, raise privacy concerns, since they enable computer surveillance of each entry. RFID cards and key fobs are becoming increasingly 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 integrate with key cards and biometric technology. Gallery See also Access control References Locksmithing Locks (security device) Doors