Abstract: An access control module restricts access to a computer system to authorized users and selectively controls each user's access to associated computer peripherals such as data storage units, printers, and communications equipment. During start-up of the computer system, a microprocessor associated with the module invokes a software routine that requests entry of a valid user identification code. In response to the code, the microprocessor retrieves from a main non-volatile storage unit pre-recorded information regarding the user's authority to access each of the peripherals, and loads the information into a secondary storage unit comprising random access memory and an address decoder adapted to retrieve data therefrom. Thereafter, the address decoder responds to each peripheral address signal generated in the input/output channel associated with the computer system and retrieves from the secondary storage unit the access information relating to the peripheral identified by the address signal.

Abstract: A device for monitoring ungrounded power distribution systems that indicates the total hazard current from the isolated power conductors to ground. A measurement signal having at least two frequency components different from the power system line frequency is applied across the combined fault impedances that occur between the power conductors and ground. Voltage responses to the measurement signal components are separated from the power system line voltage and from each other by frequency selective means. These distinct voltage responses are proportional to the fault admittance magnitude at the different measurement frequencies. The voltage responses are applied to the computational circuit whose output is proportional to the maximum fault admittance magnitude at the line frequency. A gain signal related to the imbalance of the fault impedances of the different power conductor is used to scale the previously described voltage responses.