At&t Bell Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

American Telephone and Telegraph, Co.

At&t Information Systems Inc.

David N Horn

Thomas P Bishop

Mark H Davis

Hanz Werner Herrig

Grover T Surratt

Randy D Pfeifer

Wayne R Wilcox

Lawrence A Welsch

Daniel V Peters

An arrangement for teleconferencing voice and data is provided through an arrangement that includes a voice bridge that offers individual control of the conferencing setup. The voice bridge comprises a crossbar with crosspoints that include a series connection of two switches and a resistor. One switch of each crosspoint is associated with the row of the crosspoint while the other switch of the crosspoint is associated with the column of the crosspoint. A user, connected to a selected row and column of the crossbar for the 'talk' and 'listen' functions, respectively, controls the row switches in the crosspoints connected to the user's row and the column switches in the crosspoints connected to the user's column.

Distributed control teleconferencing voice bridge

Processors (101) of a multiprocessor system (FIG. 1) communicate across bus (150) via a low-latency packet protocol featuring per-logical channel input queues (143) and output queues (144), different per-processor priorities for sending data packets (FIG. 10) and data packet-acknowledging 'quick' messages (FIG. 11), and separate buffers (923; 918) for receiving data packets and 'quick' messages, respectively. Transmitted data packets afflicted by error, receive buffer overflow, and input queue-full conditions are discarded by the receiving processor and are retransmitted by the sending processor.

Inter-processor communication protocol

An electronic circuit board electrically connected to other circuits of a data processing system by means of a bus, may be removed and re-inserted in the system without the necessity of disabling other circuits connected to the bus. A latch actuated switch provides a control signal in anticipation of circuit board removal. The control signal activates a finite state machine which seizes control of the bus after completion of any current bus communications and stops the generation of clock pulses normally required in bus communications. When contact is physically broken between the board and its corresponding connector, the finite state machine restores the bus clock pulses and relinquishes control of the bus. When a board is to be inserted in an open connector, contact between the board and the connector is sensed by the finite state machine which causes the bus to be seized and the bus clock pulses to be temporarily inhibited. When the board is fully inserted, the finite state machine restores the bus clock pulses and relinquishes control of the bus.

Method and apparatus for controlled removal and insertion of circuit

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Rumson, NJ, United States of America

David N Horn