Hotels use many different keying systems on interior doors that don't use traditional metal keys. Plastic cards embedded with various magnetic or smart devices allow guests entry via keyless systems by either swiping or waving the card by a sensor.
Magnetic stripe cards use three tracks of information stored by orienting bar magnets on the magnetized strip. When the card is slid through a lock, the sensors inside read the orientation of the information.
Integrated circuit cards store data on an internal microprocessor, or chip, located within the card. Swiping these cards allows this information to be read inside the lock.
Radio frequency cards contain a radio frequency identification chip, also called a RFID tag, which is read by radio signals emitted from from a reader or antenna. The reader decodes the data on the chip and sends this to computer, which then processes the information.
While magnetic stripe cards are the cheapest and most common, they often lose information, wear down quickly, require replacement and are recommended for use only on interior doors. Smart cards, which contain microprocessors, usually last up to two years and don't lose information as easily as magnetic stripe cards do when placed next to magnets or cell phones.
