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Massachusetts Institute of Technology

Robert G Jacobsen

David P Misunas

Thomas H Warner

Peter G Jessel

A microprocessor-based system serves as a message routing switch for communication between a number of different devices. Any device attached to the switch can communicate with any other attached device through a number of serial and parallel Input/Output ports. Communication between devices attached to the switch is in one of two formats. In a first method of communication, an attached device can be directly associated with another attached device in which case any communication from one is immediately transmitted to the other. In a second method of communication, an attached device communicates with the switch by means of fixed format packets, each of which contains a specification of its destination and error checking capabilities. This second method of communication permits examination of the validity of messages transmitted to or from the switch and enables message retransmission in the case of error.

Digital communications controller with firmware control

In a noise reduction system of the type in which an audio signal is delayed in time to permit detection of and reaction to impulse noise before application of the audio signal to a loudspeaker or the like, a transformed version of the audio signal is compared with its time-averaged value, and a resulting detection signal is processed into a control signal with blanking periods that vary as a function of corresponding impulse noise. The detection produces a response to both large impulses which stand out from the audio signal and small impulses which are hidden in the audio signal. The control signal tailors its response to the size of the impulse, blanking the audio signal substantially only for the duration of the impulse. Auxilliary circuitry is provided.

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Cambridge, MA, United States of America

Robert G Jacobsen