Bell Telephone Laboratories

At&t Information Systems Inc.

Henry S McDonald

Rajiv Bhatia

Joseph George Kneuer

Jeffrey W Reedy

Randall G Banton

Donald B Grust

Arthur D Hause

David A Poppe

Carl Christensen

Richard T Wurth

Kuang-Shin Lin

David R Johnson

A multi-stage time division switch interconnects processors communicating over one or more channels on time division lines. One of the processors is designated as a common processor to provide the switching 'mapping' information for the various stages of the switch sending the switching information to the memory and logic of each switched stage over dedicated channels which include channels on the time division line emanating from the common processor and time division channels which pass through several switches until the memory of the applicable switch is accessed.

Switching control for multiple stage time division switch

An improved ringing control circuit in a stored program telephone switching system which provides a called subscriber an interval or window of time after answering a call to send a request for special services such as identification of the number of the calling party. This time interval, initiated when ringing is tripped, delays operation of current sensitive devices which sense current flow in the subscriber line when the party answers the call. This delays completion of the connection by the systems processor which periodically scans the conditions of the current sensitive devices. A detecting device is also provided in the control circuit to detect receipt of the request for service signal during the time interval.

Arrangement for requesting service for called telephone subscribers

A centrally located stage of a time division multiplex switching network is partitioned into blocks and a separate processor is provided to control each such block. The partition is extended to the edge of the network by having each partition processor control through the network both the network equipment in adjacent stages directly coupled to the controlled block, and a preassigned portion of the remainder of the network out to the edge thereof which can be reached either through such controlled equipment or through similar equipment of other partitions. In addition, translating, scanning, and service functions are advantageously separated out of the partitioned processors and performed by separate processors that communicate through the call switching network with the partition processors and/or the network-edge ports.

Multiprocessor control of a partitioned switching network by control

A line interface unit for a digital local office for telephonic communication has a circuit connected to telemeter low-frequency signals around a line, alternating current, hybrid coupler and reinsert the same signals in the call path at the input to an analog-to-digital encoder that is coupled to a time division switching network. Each interface unit also includes circuits for multiplexing various line unit, digital, status signals with coded call signals and for demultiplexing line unit, digital, control signals from coded call signals. That network is utilized by an office common control for interconnecting various call paths with one another and for interconnecting the common control with the line interface units as required. The common control includes a time-shared digital filter for processing the telemetered signals for various office purposes.

Time division digital local telephone office with telemetering line unit

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Summit, NJ, United States of America

Henry S McDonald