At&t Bell Laboratories

Bell Telephone Laboratories

John R Colton

Lawrence Baranyai

Dominick Scordo

Robert Bruce Heick

Henry Mann

David M Simmons

Reinhard Metz

Charles D Gavrilovich

Thomas P Sosnowski

Michael S Lane

Richard N Kennedy, Jr

Teresa L Russell

John J Kulzer

Larry A Russel

This invention relates to apparatus and a method for controlling a Digital Access and Crossconnect System (DACS) from a connected toll switching system. All control messages from operations support systems (OSS) for making crossconnect changes in the DACS are first routed to the toll switch. The toll switch extracts information needed to update its database and sends a control message to the DACS. In addition, the toll switch responds to changes in traffic patterns, perhaps due to the loss of a transmission facility, to generate a crossconnect change message to the DACS to rearrange facilities for more optimum performance. Advantageously, the OSSs for DACS control and switch control is combined and the toll network is made more responsive to traffic pattern changes and to losses of transmission facilities. Also disclosed are embodiments where a DACS interconnection arrangement is integrated into a switching system, under a common control structure, in a local, central office wire center, and an embodiment where the interconnection arrangement is implemented using add/drop multiplexers connected in a fiber ring in a distributed architecture rather than using a DACS.

Method and apparatus for controlling a digital crossconnect system from

The disclosure relates to error/fault detection in signal processing systems such as those employed in a time division multiplex conferencer. The digital message samples (of the conferees) and the accompanying parity bits are delivered to a signal processor e.g., a binary arithmetic adder (10). The adder sums the message samples and this sum is coupled to a first parity tree (11), which in response thereto generates a first parity bit. The carries generated by the summing operation and coupled to a second parity tree (12) along with the message parity bits and the second parity tree generates a second parity bit therefrom. The first and second parity bits are compared (13) and if they differ a fault exists. Corrective action is taken immediately--the faulty conference 'leg' is removed from the conference connection without affecting the remaining legs in the conference or any other conference.

Fault detection arrangement for a digital conferencing system

A time division multiplex conferencer for continuously summing and outputting digital message samples received from n subscribers in n respective time slots. Message samples collected from each subscriber of a conference connection are summed during a first time frame and outputted during a second time frame. The conferencing is carried out in real time under common control to provide one or more conference-type connections between two or more subscribers. The conferencer also has the ability to establish transmit-only or receive-only connections for one or more subscribers. The conferencing is conducted in a manner that is completely independent of time slot assignments within a frame.

Time division multiplex conferencer

In a multilocation video conference system, contention for the video to be transmitted to the locations is resolved by employing so-called talker and graphics contention resolution processes. Both the talker and graphics contention processes may be overridden by manual selection of the video to be viewed at each location. In the talker contention process, the video to be transmitted is not switched until one and only one talker location is detected during a predetermined talker timing interval. In the graphics contention process, all requests for graphics transmission are rejected until one and only one graphics transmission request is detected during a predetermined graphics request timing interval. Once transmission of graphics has been assigned to a location, all other locations in the conference are transmitted the graphics video information until the location displaying graphics releases from the graphics transmission mode or there is a manual override. The location transmitting graphics information is transmitted the video from the last of the other locations selected for talker video transmission.

Multilocation video conference terminal including video switching

In a Multilocation Conference Terminal (MLCT), disruptions in the video being viewed which are caused by switching from one conference location to another are minimized by delaying switching of the video signal until a so-called get ready control signal is received from the conference location to be viewed. The conference location transmits the get ready control signal a predetermined interval prior to transmitting a so-called fast video picture update in response to a request from a Multilocation Conference Terminal (MLCT). Additional possible disruptions in the video are eliminated by minimizing the number of fast video picture updates that are used to serve a multiplicity of requests from other conference locations. When multiple MLCTs are employed in a conference, the MLCTs communicate to each other the video select modes of all the conference locations in the conference, i.e., a manual select mode or an automatic select mode. Then, the video select mode information is used to minimize the number of fast video picture updates needed to serve conference locations in the automatic select mode.

Multilocation video conference terminal including an arrangement to

In a multilocation video conference system, conference locations are dynamically added to or deleted from an ongoing conference without disrupting it. This is realized by controllably enabling or disabling communications ports assigned to the conference locations in a Multilocation Conference Terminal (MLCT). Both audio information and control channel information transmitted from a conference location assigned to a port are monitored to determine if the audio information is satisfactory and if the control channel communication is 'good'. If the audio information is unsatisfactory, it is muted and selection of the video from that location as a one-and-only-one talker is inhibited. If the control channel communication is not good the video signal from the conference location is excluded from the conference.

Multilocation video conference terminal including controllable

There is disclosed a general purpose linear time division multiplexed conference system for continuously summing and supplying digital message samples arriving in time slots within a frame. The conference system integrates both voice and data network conference connections and provides total isolation between the secondary legs of a data network connection. The host computer of a data conference connection is assigned to the lowest ordered time slot relative to the time slots assigned to secondary legs of the data conference connection. The summation of data samples accumulated from each leg of the data conference connection during a write cycle is modified during a next supply cycle after distribution to the host computer but prior to distribution to secondary legs. Modification is achieved by overwriting the summation with the data sample received from the host computer during the prior write cycle.

Linear time division multiplexed conferencer for data transfer

There is disclosed a linear time division multiplexed time slot conference for continuously summing and outputting digital message samples received from n connected telephone lines respective to m sequential time slots. The conferencer processes 256 time slots and uses prefetching techniques to reduce memory requirements to allow the circuit to be integrated into a single chip. Besides establishing conference-type connections, the conferencer has the capability to establish broadcast and monitor connections. Message samples collected from each connected line of a conference connection are summed during a first time frame and outputted during a second time frame. The conferencer includes circuitry for detecting either positive or negative overflow which could result from the summation process, and in this respect, selects an alternate message for outputting.

Linear time division multiplexed conferencer

A local alarm circuit and a remote alarm circuit carry out a plurality of failure monitoring and alarming functions for each of a plurality of digital groups (digroups), of time division multiplexed channels that are time multiplexed together on to a common bus. The local and remote alarm circuits utilize common control techniques and are of a similar circuit configuration. Each alarm circuit comprises an alarm timing store having a shared recirculating memory, and an alarm status store with a shared recirculating memory. The timing store serves to integrate and time failure indications for each of the digroups, and the status store maintains a continuing real time record of the alarm status for each digroup. When the timing store counts out a predetermined failure duration for a given digroup, the alarm status record for the digroup is changed and an alarm signal is generated. Once an alarm is registered for a digroup, the timing store then serves to integrate and time failure-free indications for the digroup. That is, it counts out a predetermined failure-free duration (after appropriate maintenance action has been taken) before it terminates the alarm state record in the status store and the alarm signal.

Common control failure alarm apparatus

The disclosed reframe circuit utilizes common control circuitry to carry out a reframing operation for any, or all, of a plurality of time division multiplexed digital data groups which are out-of-frame. An old data store is used to store a given number (m) of selected data bits, of each digital group, for two frames for framing comparison purposes. A reframe comparator serves to compare, for each digital group, the m bit output of the old data store with m data bits that are two frames later in time. A suitability store is used to record, for each group, which of the compared m data bits have had framing pattern violations and which appears as a suitable candidate for the framing bit. Based on the present set of comparisons and past suitabilities, a shift decoder searches for the framing bit within the current m-bit window until it has either marked all m bits unsuitable or has found the true framing bit within the window. If all m bits are unsuitable, the data bits of an out-of-frame digital group are shifted m bit positions, m new bits are loaded into the old data store, the suitability store is initialized for these new m bits, and the described operation is repeated. When the shift decoder finds a bit that is suitable for a given number of consecutive frames and hence is the true framing bit, the digital group is placed in-frame by shifting the data bits thereof one to m bit positions.

Common control constant shift reframe circuit

A signaling extraction circuit utilizes common control circuitry to carry out the signal extraction function for all of a plurality of time multiplexed, digital data groups (digroups), each of which comprises 24 time division multiplexed, PCM encoded channels. Each digroup uses eight bits for transmitting digital information for each channel, but the eighth bit (D8) is borrowed for signaling purposes in every sixth frame. To identify these signaling digits, signaling frame information is inserted in a digroup bit stream in the framing bit position of every other frame (i.e., the subframes). A signaling subframe pattern store comprising a shared recirculating memory serves to maintain a continuing real time record of the pattern of the signaling framing information for each digroup, as well as a test digroup. When a predetermined pattern has been recorded for a digroup (i.e., a zero subframe bit preceded by a string of exactly three ones, or a one subframe bit preceded by a string of exactly three zeros) a signal bit store is enabled to receive the D8 bits of the signaling frame which follows the recording of said predetermined pattern.

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Freehold, NJ, United States of America

John R Colton