Card reader with buffer for degraded mode

A method of operating a security system which controls access to a location and which includes a local card reader and a central controller which communicate to limit access based on card data, comprising:

• reading data stored on a card;
• evaluating the data from the card independently from the central controller;
• permitting access to a controlled location in response to the evaluation of the data from the card, with the card data remaining unchanged on the card;
• sensing at said local card reader for inablity to communicate with said central controller;
• storing card data at said local card reader during periods of inability to communicate;
• transmitting stored card data from said local card reader to said central controller when communication is possible;
• and
• receiving control signals from the central controller.

A card reader for use in a security system having a central controller and a plurality of said card readers, wherein the central controller and each card reader are electrically connected so as to each define an electrical communication system, each said card reader comprising:

• a memory;
• means for reading data stored permanently on a card, wherein said data is organized on said card so as to define first and second data segments;
• means for storing data read from said cards in said memory;
• means for sending data from said memory to said central controller at a time controlled by said electrical communication system;
• means for receiving signals from said central controller;
• means for selectively permitting access to a controlled area in response to said signals from the central controller;
• means for storing at least one authorization code;
• a local buffer;
• means coupled to said receiving means for sensing that ability to communicate with said central controller is lost;
• means for comparing a selected one of said first and second data segments with said authorization code;
• means for granting or denying access to said controlled area independent of signals from the central controller in response to said comparison of one of said first and second data segment with said authorization code, while said ability to communicate with the central controller is lost;
• means for storing the other of said first and second data segments in said local buffer during periods when said ability to communicate with the central controller is lost;
• means coupled to said receiving means for sensing that said ability to communicate with the central controller is restored;
• and
• means for transmitting the data stored in said local buffer to said central controller at a time controlled by said electrical communication system, when said ability to communicate with the central controller has been restored.

A method of operating a card reader in a security system having a central controller and plural remote card readers wherein the central controller and each of the remote card readers cooperate to each define separate electrical communication systems, and wherein each card reader has a memory and a local buffer, the method comprising:

• reading data stored permanently on a card inserted in a selected card reader, wherein said data is organized on said card so as to define first and second data segments, with read cycles initiated at a rate determined by frequency of card insertions at said reader;
• storing data read from said cards in said memory;
• sending data from said memory to said central controller at a time controlled by said electrical communication system;
• receiving signals from said central controller;
• selectively permitting access to a controlled area in response to said signals from the central controller;
• storing at least one authorization code;
• sensing that ability to communicate with said central controller is lost;
• comparing a selected one of said first and second data segments with said authorization code;
• granting or denying access to said controlled area independent of signals from the central controller in response to said comparison of said data segment with said authorization code, while said ability to communicate with the central controller is lost;
• storing the other of said first and second data segments in said local buffer during periods when said ability to communicate with the central controller is lost;
• sensing that said ability to communicate with the central controller is restored;
• and
• transmitting the data stored in said local buffer to said central controller at a time controlled by said electrical communication system, when said ability to communicate with the central controller has been restored.