Tellabs Operations, Inc.

Coherent Communications Systems Corp.

Analytics, Inc.

Barry H Bielsker

Charles A Reese

C Carson Morris

Donald A Cole

An echo canceler is connected to an ISDN Primary Rate Interface. The echo canceler is provided with an activation processor for monitoring call control messages on the D-channel and for selectively enabling or disabling echo cancellation on any of the B-channels in response to information contained within the call control messages. In particular, the activation processor decides whether to enable cancellation depending upon the Information Transfer Capability and Protocol Identification fields of the Bearer Capability portion of a call SETUP message. Additionally, the Channel Identification field of the SETUP message is used to identify the B-channel or channels affected by the SETUP message. When a channel is released, the activation processor maintains enabled echo cancellation as the default condition of the released channel. Other signal processing functions can be controlled by the activation processor in a similar manner.

Automatic echo cancellation for an integrated services digital network interface

Automatic echo cancellation for an integrated services digital network

An apparatus is provided for digital signal processing of telecommunication signals along respective transmit and receive paths of a two-way telecommunication link. The respective transmit and receive signals each include an audio data component and a timing component. Digital signal processing of at least one of the signals, such as an echo cancellation, employs information derived from the audio data component of the other signal. To compensate for differences between the respective timing components of the signals, resynchronization of each signal in terms of the timing component of the other signal is performed prior to modifying the audio data component of the other signal.

Bi-directional asynchronous telecommunication audio signal processing

Communications security between a host computer and another remote computer or terminal is ensured by a means of a two-tiered cryptographic communications security device and procedure. A master key is used to encrypt a first session key. The session key encrypted under the master key is transmitted from a remote facility to a host computer. At the host computer, the session key is decrypted and stored, a second and different session key is then generated, encrypted under the master key and transmitted to the remote facility where it is utilized as the facilities session decryptor key. Because the session key utilized for transmission of data between the remote facility and the host differs from the session key utilized for transmission of data between the host and the remote facility, communications security is increased.

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Vienna, VA, United States of America

Barry H Bielsker