Keys, optically encoded in one of more than 14 million combinations, are instantly programmed to open one or more doors through a small console at the front desk. To unlock a door, the user inserts the key into a device that resembles and replaces a traditional locking cylinder. Inside this device, infrared light passes through the key, allowing the combination to be identified. If the correct key has been inserted at the correct time of day, the user gains entry. Information about the entry is then sent to a central microcomputer, which records each event and reports events in real time. ELS's can be used to control access to any entry point where security is a factor, and they can centralize security control and generate documentation of key use. Through accurate paper audit trails, adequate control of keys and locks can be documented. Such systems have helped reduce employee theft and identify mistaken or fraudulent guest complaints about the theft of property from their rooms. Case studies illustrate how ELS's have been used at four hotels. An exhibit lists manufacturers of various types of ELS's.