Abstract: A switch is provided for use in a virtual communications system having multiple local area networks interconnected by multiple switches through a trunk, which has one or more trunk stations connected directly thereto. The switch includes a first communications port connected directly to a first local area network and a second communications port connected directly to the trunk. The first local area network is within a virtual area network configured to include a second local area network and a trunk station. A switch control detects a communication from the first local area network having a multicast address representing desired destination addresses. The switch control appends a VLAN header having a destination address different than but corresponding to the multicast address to the communication to form a VLAN communication and directs transmission of the VLAN communication to the second communication port for delivery to the multicast addressees.

Abstract: An apparatus and method for allocating the performance of applications in a networking chassis among one or more modules in the chassis. In particular, the system acts as a chassis agent for performing network management functions. The agent performs a discovery function whereby each module discovers the location and current utilization of resources and applications for itself and transmits that information to other modules, and wherein each module maintains a slot table of such information for all modules. Based on the information in the slot table, each module performs an election function for allocating applications among the various modules in the chassis. The agent uses MIBs to gather information about the chassis and to effect control on the chassis, wherein each managed object is registered both locally and remotely in a MIB tree maintained on each module, and the data is maintained locally on the module on which the managed object resides.

Abstract: A hiccup mode current protection circuit for switched mode power converters for high power applications is provided. The circuit features a comparator for comparing an indicating voltage to a reference voltage and outputting a control signal to a disabling input where the indicating voltage exceeds a predetermined voltage threshold. The control signal also causes a switch to reduce the reference voltage to ensure that the comparator continues to output the control signal regardless of a drop in the indicating voltage. The control signal is maintained by a comparator for only a predetermined time period such that the switch eventually returns the reference voltage to its pre-reduction state, allowing the comparator to discontinue outputting the control signal if the indicating voltage is below the predetermined voltage threshold.

Abstract: A voltage threshold circuit for the power factor correction stage of a power conversion system is provide. The circuit features a voltage threshold circuit with a comparator for (i) comparing a predetermined threshold voltage to the output voltage of a power factor correction stage of a power conditioner and (ii) outputting a signal if the output voltage is at least equal to the predetermined threshold voltage. The presence of the signal decreases the predetermined threshold voltage, thereby effectively changing the output voltage above which the comparator continues to output the signal.

Abstract: A method of improving modal bandwidth in computer networks using multimode optical fiber and single mode sources is disclosed in which the optical signal from a center of the optical fiber is prevented from reaching the detector. This is accomplished according to a number of different techniques including the use of opaque spots on the fiber media/fiber couplers or the use of dark-cored fiber couplers. These configurations prevent pulse splitting that occurs in single mode source/multimode fiber systems by preventing light from the multimode fiber's center from interfering with the detector. When this is achieved, the detector is insulated from the effects of pulse splitting, supporting increased data rates by increasing the modal bandwidth.

Abstract: Method and apparatus for establishing connections in a switch-based communications network for multicast traffic. A source receives a multicast packet on an access port from a source host, determines a group address in the multicast packet, and composes and sends a “sender present” message to other switches on its network ports. The receiving switches determine whether a local host wishes to join the group and if so, send a map message back toward the source switch on a predetermined path between the receiving switch and the source switch. A map message may terminate at a switch on the path that already has a connection for this group/source pair, and join into this connection as an additional output port. In this manner, a “signal out, connect back” method is provided for establishing a connection path from the sender to multiple receivers.

Abstract: A switch is provided for use in a communications system for transmitting traffic from a first user to a second user. The first and the second users are interconnected by a primary communications path and a redundant communications path. The switch includes a first port configured to receive hello communications indicative of a proper operation of the primary communications path and a second port for receiving data communications. A switch control monitors the receipt of the hello communications, directs the forwarding of received data communications up to a threshold capacity and, if the received data communications exceed the threshold capacity, drops at least a portion of the received data communications such that forwarded data communications are below the threshold capacity.