Abstract: A network over which a medium is transferred. The network includes S core rings. Each core ring can be modeled as a set of nodes interconnected by links, where S is greater than or equal to 4 and is an integer, each said core ring having at least N nodes, where N is greater than or equal to 4 and is an integer. Each node/link is configurable in terms of directing the medium from a given source toward a given destination, and where each of the core rings is directly connected by means of k spanning links, where k is greater than or equal to 2, so as to comprise a spanning ring to at least a second and a third of the other core rings. The combinations of core rings spanned by each core ring is such that there is a path comprised of links and nodes from each node on any core ring to any other node on any other core ring. A method for transferring a medium.

Abstract: A network over which a medium is transferred. The network includes S core rings. Each core ring can be modeled as a set of nodes interconnected by links, where S is greater than or equal to 4 and is an integer, each said core ring having at least N nodes, where N is greater than or equal to 4 and is an integer. Each node/link is configurable in terms of directing the medium from a given source toward a given destination, and where each of the core rings is directly connected by means of k spanning links, where k is greater than or equal to 2, so as to comprise a spanning ring to at least a second and a third of the other core rings. The combinations of core rings spanned by each core ring is such that there is a path comprised of links and nodes from each node on any core ring to any other node on any other core ring. A method for transferring a medium.

Abstract: A controller for a nonblocking broadcast switching network comprising an input stage, an output stage, and a middle stage. The input stage has N.sub.1 or n.sub.1 r.sub.1 input ports and r.sub.1 switches, where n.sub.1 .gtoreq.2 and r.sub.1 .gtoreq.1 and are integers. The network also includes an output stage. The output stage has N.sub.2 or n.sub.2 r.sub.2 output ports and r.sub.2 switches, where n.sub.2 .gtoreq.2 and r.sub.1 .gtoreq.1 and are integers. There is also a middle stage. The middle stage has m switches, where ##EQU1## The m switches are in communication with the r.sub.1 switches and r.sub.2 switches. The middle stage of m switches has L inputs, where L.gtoreq.r.sub.1 and is an integer, and J outputs, where J.gtoreq.r.sub.2 and is an integer, corresponding to the n.sub.1 input ports and n.sub.2 output ports, x or fewer of the m switches, where 1.ltoreq.x.ltoreq.

Abstract: The present invention pertains to a nonblocking broadcast switching network. The network comprises an input stage. The input stage has N.sub.1 or n.sub.1 r.sub.1 input ports and r.sub.1 switches, where n.sub.1 .gtoreq.2 and r.sub.1 .gtoreq.1 and are integers. The network is also comprised of an output stage. The output stage has N.sub.2 or n.sub.2 r.sub.2 output ports and r.sub.2 switches, where n.sub.2 .gtoreq.2 and r.sub.1 .gtoreq.1 and are integers. There is also a middle stage. The middle stage has m switches where m is an integer and, where ##EQU1## The m switches are in communication with the r.sub.1 switches and r.sub.2 switches. The middle stage of m switches has L inputs, where L.gtoreq.r.sub.1 and is an integer, and J outputs, where J.gtoreq.r.sub.2 and is an integer, x or fewer of the m switches, where 1.gtoreq.x.gtoreq.min{n.sub.2 -1, r.sub.

Abstract: A method and apparatus for achieving fault tolerance in a computer system having at least a first central processing unit and a second central processing unit. The method comprises the steps of first executing a first algorithm in the first central processing unit on input which produces a first output as well as a certification trail. Next, executing a second algorithm in the second central processing unit on the input and on at least a portion of the certification trail which produces a second output. The second algorithm has a faster execution time than the first algorithm for a given input. Then, comparing the first and second outputs such that an error result is produced if the first and second outputs are not the same. The step of executing a first algorithm and the step of executing a second algorithm preferably takes place over essentially the same time period.

Abstract: The present invention pertains to a broadcast network. The broadcast network comprises N transmit stations, with each transmit station being capable of transmitting a signal and N being an integer .gtoreq.1. There are also M receive stations, where M is an integer .gtoreq.2; I switching stages where I is an integer .gtoreq.0 and a broadcast hub. The broadcast hub and I switching stages are connected such that they are capable of linking the N transmit stations to the M receive stations so that any one of the N transmit stations can transmit a signal to L of the receive stations, where L is an integer and 2.ltoreq.L.ltoreq.M, but each receive stations can receive a signal from only one of the N transmit stations at any given time. The broadcast hub and switching stages link more than one of the N transmit stations to desired receive stations at any given time.

Abstract: The present invention pertains to a conferencing network. The conferencing network is comprised of a ring array comprised of K conferencing modules, where K is greater than or equal to 3 and is an integer. The K conferencing modules are capable of being in desired states. The conferencing network also includes means for controlling the ring array such that the conferencing modules are placed in the desired states. Switching stages comprised of switches can also be implemented into the conferencing network.

Abstract: A rearrangeable fully available multistage switching network having N.sub.T inputs and M.sub.T outputs, preferably where N.sub.T =M.sub.T, comprising a plurality of switching elements arranged in an array of .theta. stages, where .theta..gtoreq.3. The inner groups of stages define a plurality of nested modules where each of the switches in an outer stage is connected to associated subordinate inner modules such that at least one set, f.sub.i, of said connections between stages is redundant, that is, greater than 1.