The invention provides, in one aspect, an access control system that comprises an access control panel coupled to an access control expansion box. The access control panel includes one or more access control boards disposed within a first rack-mount enclosure, each control board providing at least an interface for monitoring and/or controlling access to one or more building entry points or zones via associated sensors and/or intrusion prevention devices, collectively, “security devices.” The access control expansion box includes a plurality of input/output (I/O) boards disposed within a second rack-mount enclosure. The I/O boards provide an interface for at least (i) sending signals received from one or more additional security devices to the control boards, and/or (ii) sending signals received from the control boards to one or more of the additional security devices.