The NSC-100 is only a sub-controller, it does not hold cardholder data, all the cardholder data is kept on the main controller. if the NSC-100 has lost connectivity to the main controller it will follow what the door is set up for during off-line mode, default is set to facility code. You can find more information about the NSC-100 in the hardware manual, http://www.ooaccess.com/download/manuals/HW_Manual.pdf You can find more on off-line mode in the user manual, http://www.ooaccess.com/download/manuals/DNA_Fusion-U.pdf.