American Telephone and Telegraph, Co.

At&t Information Systems Inc.

John M Nichols

Richard A Windhausen

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

A data transmission flow control arrangement for controlling the flow of data packets to a network as tramsmitted by one or more data transmitting and receiving devices via an interface is disclosed. The disclosed flow control arrangement provides circuitry in the interface responsive to the storage capacity of a buffer included in the interface. If the buffer contains sufficient space to store a data packet of maximum length, data transmissions continue unencumbered. However, if the buffer contains insufficient space to accomodate a data packet of maximum length, the specialized circuitry of the interface responds to this condition and applies a signal to all of the associated transmitting and receiving devices of the interface. The jamming signal simulates the conditions associated with a busy network and therefore, inhibits the transmission of data from any of the associated transmitting and receiving devices. The specialized circuitry of the interface terminates the application of the jamming signal to all associated transmitting and receiving devices when the buffer again contains sufficient space to accommodate a data packet of maximum length.

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Arvada, CO, United States of America

John M Nichols