American Telephone and Telegraph, Co.

At&t Information Systems Inc.

Richard A Windhausen

John M Nichols

David L Bauer

Larry D Bowyer

David M Ruby

An arrangement for securing data transmissions to and from one data device from among a plurality of data devices sharing a common interface is disclosed. In a data communication network, a master communication bus connects to a plurality of data transmitting and receiving devices via a single interface. The disclosed arrangement provides circuitry in the common interface which generates a jamming signal to all devices connected to the interface except for that one device which is either transmitting or receiving a data-transmission. The jamming signal inhibits all the connected devices from monitoring and detecting the data transmission processes of the interface. The one transmitting and receiving device is enabled to either transmit or receive data during the generation of the jamming signal which ensures a secure data transmission and prevents 'eavesdropping' by the other devices. The jamming signal is removed at the conclusion of the data transmission to or from the one device.

Data transmission security arrangement for a plurality of data stations

There is disclosed a port communication method and apparatus for controlling system controller communications with port circuits of the system. The port communication apparatus generates commands to port module interfaces, interposed between the controller and port circuits, in a predetermined order and receives acknowledgement signals therefrom. Thereafter, the port interfaces concurrently collect data from the associated port circuits and transmit this data in response to a subsequent read command from the port communication apparatus. In one embodiment the port communication apparatus includes a programmable microcode routine which generates the commands using input parameters which are specified in various registers and in the microcode program call.

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Thornton, CO, United States of America

Richard A Windhausen