Gte Communication Systems Corporation

Ag Communication Systems Corporation

Arthur L Walsh

John S Young

James B Black

James F Hoff

Donovan A Bruce

Steve A Wright

Tom Perry

Gary Wiren

Mike Gilbert

Mauro Cordani

An Integrated Services Digital Network module includes a time division multiplexed switching network. Subscribers are connected to the time division multiplex network via a number of facility interface cards. These facility interface cards provide for two wire subscriber connection, four wire subscriber connection, T1 line connection and for three port conferencing arrangements. Originating and terminating multiplexers connect the facility interface cards to the time switching network. Another subsystem provides protocol interfaces for HDLC channels. Another subsystem provides interface to central office switching systems. Lastly, a general purpose computer and file computer system provide for the storage of database and form maintenance functions. Each subsystem is controlled via processor which is linked with each of the other processors by an ethernet local area network. This system provides both Primary Rate (23B+D) and Basic Rate (2B+D) interfaces to the subscribers.

Integrated services digital network module

An echo cancellation arrangement is provided for decreasing the 'singing' of a connection of a large number of telephone subscribers in a conference calling arrangement. This arrangement includes a means for inserting quiet code during time when the voice samples of incoming PCM data are zero or below a predetermined minimum threshold level. This helps decrease the amount of feedback which is amplified and output through the codec/filter to the listeners through the PCM network. An attenuation arrangement is also included which decreases the level of a summed signal of a summing node of the conference circuit. This sum signal is the combination of each of the conferees' speech. Attenuation of this signal prohibits excessive coupling of amplified feedback to each of the listening conferees.

Digital voice switch for a multi-port conference circuit

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Phoenix, AZ, United States of America

Arthur L Walsh