Abstract: A security access management system for a packet switched data communications network has access management apparatus operatively associated with the packet switches at each entry point of the network. The access management apparatus includes an administrative host processor for examining user terminal authorization information in packets received at the associated packet switch for transmission through the network to destination addresses for the packets. A database associated with the administrative host stores information including levels of authorization of the user terminals for the respective entry point of the network for access to specified destinations, as pre-assigned by the network customer.

Abstract: A vent tube having a first branch and a second branch for use in a cryogenic container through which the interior of the container is communicated to the atmosphere. The cryogenic container is adapted to receive a fixed volume of cryogenic fluid at a uniform temperature and density. In a filling operation, the first branch of the vent tube contacts the cryogenic fluid and carries a portion of the fluid to the atmosphere to inform an operator that the capacity of the container has been reached. After the container is filled, the temperature in the stored cryogenic fluid rises. As the temperature changes, distinct stratified layers of fluid of different densities and temperatures can be measured in the container. The change in temperature causes the cryogenic fluid to expand and submerge the adjacent first branch of the vent tube.