Multilocation video conference terminal including video switching contention control

Abstract

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.

Claims

What is claimed is:

1. An apparatus for transmitting video signals to a plurality of remote locations, wherein each of the remote locations is or includes at least one conference location and each conference location generates a graphics transmission request message signal when a graphics video signal transmission is desired from the conference location,

means for resolving contention among the remote locations for the video signal to be transmitted from a conference location to other locations including

means for determining one conference location of said plurality of remote locations generating a graphics request message signal with an absence of graphics request message signals from all the other locations during a predetermined graphics timing interval; and

means for transmitting the video signal from said determined one conference location to all the other remote locations.

2. Apparatus as defined in claim 1 wherein said means for resolving contention further includes means for providing each conference location requesting graphics transmission an indication of whether its request is granted or denied.

3. In apparatus for transmitting video signals to a plurality of remote locations, wherein each of the remote locations is or includes at least one conference location and each conference location generates a graphics transmission request message signal when graphics transmission is desired and a talker message signal when a talker is detected at the conference location,

means for selecting one conference location of said plurality of remote locations having a talker with an absence of talkers at the other locations during a predetermined talker timing interval,

means for selecting one conference location of said plurality of remote locations generating a graphics request message signal with an absence of graphics request message signals from all the other locations during a predetermined graphics timing interval, and

means for selecting a video signal from said plurality of remote locations to be transmitted to said remote locations according to a prescribed priority including if a conference location requesting graphics transmission has been selected, a video signal from said selected graphics conference location is transmitted to all locations except said selected graphics conference location and a last previous selected talker conference location video signal other than that from said selected graphics conference location is transmitted to said selected graphics conference location, and if a graphics conference location has not been selected, a video signal from said selected talker conference location is transmitted to all of said remote locations except said selected talker conference location and said last previous selected talker video signal other than said selected talker video signal is transmitted to said selected talker conference location.

4. Apparatus as defined in claim 3 wherein said talker conference location selecting means includes means for inhibiting switching of the video signal being transmitted from said selected talker conference location until another talker conference location generating a talker message signal with an absence of talker message signals from all other locations during a current or subsequent one of said predetermined talker timing intervals is detected.

5. Apparatus as defined in claim 4 wherein said talker timing interval is at least 400 milliseconds.

6. Apparatus as defined in claim 3 wherein said graphics location selecting means includes means for providing each location requesting graphics transmission an indication of whether its graphics transmission request has been granted or denied.

7. Apparatus as defined in claim 6 wherein said graphics conference location selecting means further includes means for denying all requests for graphics transmission until a graphics transmission request message signal from a location is detected with the absence of graphics request message signals from all other locations during said predetermined graphics request timing interval.

8. Apparatus as defined in claim 7 wherein said graphics transmission request timing interval is at least 400 milliseconds.

9. In apparatus for transmitting video signals to a plurality of remote locations, wherein each of said remote locations is or includes at least one conference location and each conference location generates a talker status signal indicative of the talker state at the conference location, a graphics request signal indicative of the graphics transmission request state at the conference location and a video selection signal which can select the video signal from the other conference locations to be transmitted to the conference location,

means responsive to the talker status signals from the plurality of locations for selecting one of said conference locations having a talker with an absence of talkers from all other locations during a predetermined talker timing interval,

said talker conference location selecting means generating signals representative of a current selected talker conference location and at least a last previous selected talker conference location,

means responsive to the graphics request signals from the plurality of locations for selecting one of said conference locations generating a graphics request signal with an absence of graphics request signals from the other locations during a predetermined graphics request timing interval, and

means responsive to outputs from said talker selecting means, from said graphics selecting means and to video selection signals from said conference locations for selecting the video signal to be transmitted to each of said locations from the other locations according to a prescribed priority including, if a video selection signal is received from the conference location, the video signal from a conference location identified by the video selection signal is transmitted to that location, if no video selection signal is received and a conference location requesting graphics transmission has been selected, the video signal from said selected graphics conference location is transmitted to all locations except the said selected graphics conference location and the current selected talker conference location video signal if it is not that from said selected graphics conference location is transmitted to said selected graphics conference location, if the current selected talker conference location is the graphics conference location a last previous selected talker conference location video signal is transmitted to the selected graphics conference location, and if no video selection signal is received and a graphics conference location has not been selected, a video signal from said current selected talker conference location is transmitted to all the locations except said selected talker conference location and the last previous selected talker conference location video signal is transmitted to said selected talker conference location.

10. Apparatus as defined in claim 9 wherein said talker selecting means includes means for inhibiting the start of said talker timing interval until the talker conference location is selected.

11. Apparatus as defined in claim 9 wherein said talker selecting means includes means for starting said talker timing interval only when a conference location having a talker with an absence of talkers from all other locations is detected and means for stopping said talker timing interval when none or more than one conference location having a talker is detected.

12. Apparatus as defined in claim 11 wherein said talker timing interval is approximately 400 milliseconds.

13. Apparatus as defined in claim 11 wherein said graphics request timing interval is approximately 400 milliseconds.

14. Apparatus as defined in claim 11 wherein said remote locations include conference locations and can include other apparatus for transmitting video signals to a plurality of remote locations.

15. Apparatus as defined in claim 14 wherein said video signals are transmitted in digital form.

Description

RELATED APPLICATIONS

U.S. patent applications Ser. No. 545,761 (J. R. Colton et al), Ser. No. 545,461 (J. R. Colton et al), Ser. No. 545,363 (D. Scordo), Ser. No. 545,364 (D. Scordo), and Ser. No. 545,162 (D. Scordo) were filed concurrently herewith.

TECHNICAL FIELD

This invention relates to audio-visual conferencing systems and, more particularly, to a system for controllably connecting a plurality of conference locations together including video switching contention resolution.

BACKGROUND OF THE INVENTION

Heretofore, analog signals were used in multilocation conference arrangements to transmit both video and audio information. Consequently, when the video to be viewed is switched from one conference location to another the entire video picture was present and switched. In more recent conference arrangements, digital signals are employed to transmit the video information which do not usually contain complete picture information. Indeed, the digital signal usually includes only changes in the scene being viewed. Therefore, upon switching the digital signal, there is some disruption in the picture being viewed until the complete picture information is obtained.

None of these prior known arrangements resolve contention among multiple talkers at different conference locations or multiple requests for graphics transmission from different conference locations.

In one known arrangement, the video signal to be transmitted to conference locations is selected to be from a location having the first talker. While in another known arrangement the video is selected from the location having the loudest talker.

Problems arise in these prior arrangements when a number of conferees at different locations are concurrently talking. Indeed, the first talker or the loudest talker may not be the "right" or desired talker. This may lead to unnecessary switches in the video being transmitted before the "right" talker is selected. Such unnecessary switching adds undesirable disruption in the video being viewed. This is especially true in those conference arrangements which use digital signals to transmit the video information.

It is also important that after an interval of concurrent talkers the single retaining talker should be viewing a conference location he or she is responding or otherwise talking to and not some other location. This desired result may not be obtained in the prior known arrangements which have no mechanism for resolving contention among the locations for the video to be viewed.

Similar problems arise in conference arrangements including the transmission of graphics information. In one known conference arrangement, it is possible that during an interval of concurrent graphics transmission from different locations some of the conference locations may be viewing graphics information transmitted from one location while other conference locations may be viewing graphics transmitted from another location. This, of course, can be extremely undesirable. Additionally, multiple switches of the video being transmitted may be required before arriving at the "right" graphics transmission location. Again, in conference arrangements using digital transmission of the video information such unnecessary switching is undesirable because of the resulting disruptions in the video being viewed.

SUMMARY OF THE INVENTION

Contention among conference locations for the video information to be transmitted to the locations is resolved, in accordance with an aspect of the invention, by employing talker and graphics contention resolution processes.

A talker contention process selects, in accordance with an aspect of the invention, the video to be transmitted to the other locations from a location determined to have the one-and-only-one talker during a predetermined talker timing interval. The process inhibits switching the video information being transmitted until a different one-and-only-one talker location is detected during the predetermined talker contention timing interval, or a location starts to display graphics. The video information from the last selected talker location is transmitted to the presently selected one-and-only-one talker location.

A graphics contention process selects, in accordance with an aspect of the invention, the graphics information to be transmitted to the other locations by first rejecting all requests for graphics transmission from the locations until one-and-only-one graphics request is detected during a predetermined graphics timing interval. Once transmission of graphics information is assigned to a location, the other locations in the conference are transmitted the graphics video information until the location displaying the graphics information releases from the graphics tansmission mode. The location transmitting graphics information is transmitted video information from the (current) last of the other locations determined to be the one-and-only-one talker location.

Each conference location can normally select the video information to be transmitted to it. Thus, the talker and graphics contention processes can be manually overridden.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detailed description of an illustrative embodiment taken in connection with the appended figures in which:

FIG. 1 shows in simplified block diagram form a system arrangement including a Multilocation Conference Terminal (MLCT) incorporating an embodiment of the invention;

FIG. 2 depicts the VTS signal data format used in the system of FIG. 1;

FIG. 3 illustrates the cross connect frame format used in the system of FIG. 1;

FIG. 4 shows in simplified block diagram form details of microprocessor system 101 employed in the system of FIG. 1;

FIG. 5 depicts in simplified block diagram form details of transmission facility interface 104 used in the system of FIG. 1;

FIG. 6 shows in simplified block diagram form details of cross-connect 102 employed in the system of FIG. 1;

FIG. 7 illustrates in simplified block diagram form details of time multiplexed switch 601 used in cross-connect 102 of FIG. 6;

FIG. 8 shows in simplified block diagram form details of N.times.N switch 602 used in cross-connect 102 of FIG. 6;

FIG. 9 illustrates the cross-connect 102 audio and video time slot assignments utilized in effecting an aspect of the invention;

FIG. 10 shows in simplified block diagram form details of bridge 103 used in the system of FIG. 1;

FIG. 11 depicts in simplified block diagram form details of bridge input circuit (BOC) 1001 used in bridge 103 of FIG. 10;

FIG. 12 illustrates the output frame format of the audio encryption process which is useful in describing aspects of the invention;

FIG. 13 illustrates timing diagrams useful in describing the encryption and decryption process;

FIG. 14 shows in simplified block diagram form details of audio decryptor (DEC) 1002 used in bridge 103 of FIG. 10;

FIG. 15 illustrates a flowchart of the decryptor program routine for the common control operation of decryptor 1002 to controllably decrypt the incoming audio and control information of bridge 103;

FIGS. 16, 17, 18 and 19 when connected as shown form a flow chart of the PADEC sub-routine used in the decryptor routine of FIG. 15;

FIGS. 20 and 21 connected as shown form a flow chart of the CENCHR sub-routine used in the decryptor routine of FIG. 15;

FIG. 22 shows in simplified block diagram form details of audio bridge 1003 employed in bridge 103 of FIG. 10;

FIGS. 23, 24, 25 and 26 when connected as shown form a flow chart of a program routine for controllably operating DSP 2201 in audio bridge 1003 of FIG. 22;

FIGS. 27, 28, 29 and 30 when connected as shown form a flow chart of a program routine for controllably operating DSP 2202 in audio bridge 1003 of FIG. 22;

FIG. 31 is a flow chart of a DSP control (DSPCTL) program task for operating host processor 2203 to interact with digital signal processors (DSPs) 2201 and 2202 in audio bridge 1003 of FIG. 22;

FIG. 32 is a flow chart of a noise guard program (NGRD) sub-routine used in the DSPCTL program task of FIG. 31;

FIG. 33 shows in simplified block diagram form details of audio encryptor (ENC) 1004 employed in bridge 103 of FIG. 10;

FIGS. 34, 35 and 36 when connected as shown form a flow chart of program routine ESCVC to effect common control of the mixed audio information from audio bridge 1003;

FIG. 37 is a flow chart of the PAENC sub-routine used in the ESCVC program routine of FIGS. 34, 35 and 36;

FIG. 38 depicts in simplified block diagram form details of bridge output circuit (BOC) 1005 used in bridge 103 of FIG. 10;

FIG. 39 shows in simplified block diagram form details of control processor (CF) 1006 used in bridge 103 of FIG. 10;

FIG. 40 is a flow chart of program routine XPCTL for operating control processor 1006 of FIG. 39 to control communications to audio decryptor 1002, audio bridge 1003 and audio encryptor 1004;

FIG. 41 is a flow chart of sub-routine PREST used in the XPCTL program routine of FIG. 40;

FIGS. 42, 43, 44 and 45 when connected as shown form a flow chart of the PRNLA sub-routine employed in the XPCTL program routine of FIG. 40;

FIG. 46 is a flow chart of the PRDENT sub-routine employed in the XPCTL program routine of FIG. 40;

FIG. 47 illustrates the relationship among the program tasks that perform the video selection algorithm and the fast update algorithm;

FIGS. 48, 49 and 50 when connected as shown form a flow chart of steps performed in the new talker process (NTP) task by control processor 1006 of FIG. 39;

FIG. 51 is a flow chart of the CONTEND sub-routine used in the NTP program task of FIGS. 48, 49 and 50;

FIG. 52 is a flow chart of the NTSAVE sub-routine used in the NTP progam task of FIGS. 48, 49 and 50;

FIGS. 53, 54, 55 and 56 when connected as shown form a flow chart of the steps performed in the new graphics process (NGP) program task by control processor 1006 of FIG. 39;

FIG. 57 is a flow chat of the GRACK sub-routine used in the NGP program task of FIGS. 53, 54, 55 and 56;

FIGS. 58 and 59 when connected as shown form a flow chart of the steps performed in the video selection (VSEL) program task by control processor 1006 of FIG. 39;

FIGS. 60 and 61 when connected as shown form a flow chart of the steps performed in the fast update generator (FUGEN) program task by control processor 1006 of FIG. 39;

FIGS. 62 and 63 when connected as shown form a flow chart of the steps performed in the fast update monitor (FUMON) program task by control processor 1006 of FIG. 39;

FIGS. 64 and 65 when connected as shown form a flow chart of the steps performed in the video switch (VSWCH) program task by control processor 1006 of FIG. 39; and

FIG. 66 is a flow chart of the SWITCHLK sub-routine used in the VSWCH program task of FIGS. 64 and 65; and

FIGS. 67 and 68 when connected as shown form a flow chart of steps performed in facility administrator (FADMIN) program task by control processor 1006 of FIG. 39.

DETAILED DESCRIPTION

General

The Multilocation Conference Terminal, hereinafter referred to as MLCT, is employed to establish and control a multilocation audiovisual teleconference in a Video Teleconferencing Service, hereinafter referred to as VTS, for conferences involving a plurality of VTS conference rooms. Accordingly, FIG. 1 shows in simplified block diagram form a system arrangement including a pluralty of MLCT's, namely, MLCTs 1 through Y and a plurality of conference rooms, namely, rooms 1 through M, which may be controllably interconnected via the MLCT's and transmission facilities 10. Each of MLCTs 1 through Y includes a plurality of VTS communication ports, associated with data links 106-1 through 106-N, for interconnecting up to N rooms via transmission facilities 10. Transmission facilities 10 include both terrestrial communication channels and/or satellite channels. Additionally, facilities 10 also include arrangements for interconnecting one or more of the conference rooms, i.e., conference locations, to an associated MLCT for establishing a conference. These connections may be established manually or via switching apparatus, for example, a digital cross connect arrangement. When satellite channels are deployed a multiplicity of MLCTs are used to reduce the number of end-to-end satellite hops to a maximum of one. In the satellite mode of operation, the MLCTs form a distributed conferencing control structure.

A number of conference configurations are realizable including one or more MLCTs. For example, a single MLCT may be used to include up to N=6 rooms in a conference over either local or long-haul terrestrial communication facilities. While it is possible to use only one MLCT in an all terrestrial confererence, it is not necessary to do so. Two MLCT's can be connected terrestrially, allowing savings of transmission facilities. In a mixed satellite/terrestrial conference network, distributed conferencing is used with a MLCT being associated with each satellite earth station. Satellite and terrestrial connections remain unchanged during an ungoing conference.

Each of MLCTs 1 through Y provides a time-space-time switching function and includes microprocessor system 101, digital cross connect 102, bridge 103, transmission facility interface 104 and a plurality of data terminal ports 105-1 through 105-T. Data terminals may be connected to data terminal ports 105-1 through 105-T for manually providing teleconference setup information including VTS port assignment and other information needed for the ongoing conference. Where an operations support system or other reservation service computer is available, the data terminal ports are used to connect the MLCT thereto for carrying out the necessary conference setup and maintenance procedures.

As described hereinafter each MLCT provides audio mixing and video switching of encrypted digital VTS signals which are supplied via VTS ports and data links 106-1 through 106-N, respectively, to transmission facilities 10 and, in turn, to associated ones of rooms 1 through M and/or to another MLCT. In this example, each MLCT includes six (6) VTS ports, i.e., N=6.

Each of conference rooms 1 through M includes known audio and video equipment. For example, each room includes video monitors and cameras 120, speakers and microphones 121, audio detectors 122, picture processor 123, rooms controls 124 and room controller 125. Rooms substantially identical to rooms 1 through M are presently commercially available for point-to-point audiovisual conferences. Room controller 124 is arranged to respond to an auxiliary control channel signal in the VTS signal from an associated MLCT for controlling picture processor 123 in accordance with aspects of the invention as will be described below. Picture processor 123 is commercially available from Nippon Electric Corporation and is described in Western Electric Company KS-22456 specification. U.S. Pat. No. 3,601,530 discloses a video conference arrangement using voice-switched cameras in a conference room. Further details of the point-to-point conference room are broadly described in an article by Mr. Bernard A. Wright entitled, "The Design and Provisions of PICTUREPHONE Meeting Service (PMS) Conference Centers for Video Teleconferencing", in the IEEE Communications Magazine, pages 30-36, March 1983. Also see an article by Audrey J. Kames and W. Gordon Heffron entitled, " Human Factors Design of PICTUREPHONE Meeting Service" in GLOBECOM '82 Conference Record, Volume 3, pages 976-981, November 1982 for a broad overview of the commercially available point-to-point video teleconferencing service.

As indicated above, the MLCTs are interconnected via transmission facilities 10 to associated ones of rooms 1-M and/or another one of the MLCTs through VTS ports 501-1 through 501-N (FIG. 5) and data links 106-1 through 106-N, respectively. The VTS signals are transmitted over one or more time division multiplexed channels, for example, T1 lines, depending on the data rate being employed. In this example, the data rates are selectable at 1.544, 3.088 or 6.176 Mb/sec. In a specific embodiment, two T1 lines are used having the 3.088 Mb/sec data rate with each T1 line having an incoming data link and an outgoing data link. The VTS data format is shown in FIG. 2. One of the T1 lines, designated DS-1 No. 1 carries encoded audio and control channels in addition to video data. The other T1 lines, designated DS-1 No. 2 through DS-1 No. 4 carry only video data. The T1 lines do not have standard DS-1 formats except for framing bits Ft.

The format for DS-1 No. 1 is a combination of three groups of information; one associated with the video signal; another with audio; and another with the control data channel. The control group consists of a single C-bit per frame located in word 1 bit 4, as shown in FIG. 2. The C-bit implements an 8 Kb/sec data link between the MLCT and the remote location communicating to it, i.e., either a room or another MLCT. The audio group consists of 16 audio bits, A1 to A16, a D-bit, as well as "1"s in the shown bit positions, all within the first three words of DS-1 No. 1. The A-bits represent two samples per frame of mu-255 coded audio. Bits A1 through A8 are audio bits belonging to a first sample of the audio signal. Bits A9 through A16 are audio bits belonging to the second sample of the audio signal. The audio may be encrypted or transmitted "on the clear". The D-bit is used for synchronization of the audio encryptor 1004 and decryptor 1002 described below.

The first three words of the DS-1 No. 1 contain fixed "1"s in the shown position to maintain the required "1"s density during these words for all possible codes transmitted. The remaining bits in DS-1 No. 1, i.e., FD, X, X, and those of DS-1 No. 2 through DS-1 No. 4 contain video information. The MLCT does not process these remaining bit locations aside from maintaining their relative position throughout its switching function. Indeed, except for the information included in the C-bit position, the VTS data format is essentially identical to that employed in the existing point-to-point teleconferencing service available through American Telephone and Telegraph Company.

MLCT Operation--General

A Multilocation Conference Terminal (e.g., MLCT1, FIG. 1) located in a Video Teleconferencing Service (VTS) is connected via transmission facilities 10 to conference locations, i.e., rooms and other MLCTs dependent on the conference being set up.

The MLCT is always in one of the following modes:

Standby (SBY)

In the standby mode the MLCT is not processing a conference. It is continually performing internal diagnostics to ensure that it is fully operational.

Sender's Choice (SC)

A MLCT in the SC mode is set up to operate a SC conference.

Viewer's Choice (VC)

A MLCT in the VC mode is set up to operate a VC conference.

No MLCT mode changes are allowed while the MLCT is processing a conference. To change modes the MLCT must first be removed from the conference.

The steps to set up the MLCT for a conference are as follows:

1. Enter command(s) into the MLCT through an input terminal connected to one of input ports 105-1 through 105-T to place it in the desired mode for the conference (VC,SC) and to define the MLCT's ID in the conference.

2. Setup transmission connections to the MLCT required for the conference.

3. Enter command(s) into the MLCT to assign the VTS ports as either:

a. connected to a room (specify room ID).

b. a broadcast link (outgoing transmission path to all other MLCTs in the conference) and/or a MLCT link (incoming transmission path from another MLCT, specify that MLCT's ID).

Once these steps are completed the conference is in progress and the MLCT will automatically set up and maintain communication with its serving rooms, i.e., rooms associated to it, and other MLCTs.

If communication over a VTS port connected to a room, e.g., room I, is lost (or is never established in the first place) the MLCT operates the conference without room I. No other room can view room I. The audio transmitted by room I is not muted unless audio decryptor 1002 (FIG. 10) detects a facility failure in the audio signal incoming from room I. The video transmitted to room I is selected by assuming that room is in the automatic video switching (AVX) mode. Thus, room I essentially becomes a spectator. Room I views a new talker room or a new graphics room as described below. The other rooms hear room I if its audio signal is not muted, but they cannot view room I.

If communication over a broadcast link or MLCT link is lost (or is never established in the first place) the MLCT operates a conference for only the rooms that it serves.

Configuration changes to a conference already in progress are realized as follows:

1. If any of the MLCT's room, broadcast, or MLCT links are to be removed, then:

a. Command(s) must be entered into the MLCT that unassign those links.

b. The port connections to be removed are taken down.

2. If any room, broadcast, or MLCT links are to be added to the conference, then:

a. The port connections just assigned are set up.

b. Command(s) must be entered into the MLCT to assign each new port as connected to a room or as a broadcast link and/or MLCT link.

Any number of configuration changes can occur during a conference.

The microprocessor system (MS) 101 (FIG. 1) maintains control of the MLCT. Commands are entered through the links 105-1 through 105-T into the MS 101. The MS 101 interprets these commands and issues signals to set up the other components of the MLCT. The MS 101 is responsible for downloading the proper program code into bridge 103 when any MLCT mode change is performed and for informing the bridge on all the conference attributes (MLCT's ID and link assignments). MS 101 cannot communicate directly with other MLCTs or any room controllers.

Bridge 103 computes the weighted sums of the audio signals, receives the control signals that come over the incoming links from the rooms and other MLCTs, generates the control signals that are transmitted to the rooms and other MLCTs, signals MS 101 to execute video switches, and monitors the links to detect facility failures in the control and audio signals.

MS 101 and bridge 103 interact during a conference to perform two primary functions. Bridge 103 directs MS 101 to perform switching of the video signals. MS 101 and bridge 103 keep each other informed of link failures.

Cross-connect 102 and transmission facility interface 104 provide bridge 103 with audio and control signals, receive conferenced audio and control signals from bridge 103 and perform the switching of the video signals under the control of the MS 101.

The MLCT can be in one of three modes (SBY, SC, or VC) as described above. Bridge 103 can be in one of four states. Three of the bridge states correspond to the MLCT modes (SBY, SC, and VC). Bridge 103 enters the fourth state, called the kernel state, while MS 101 is downloading a new program code. The MLCT's mode and bridge state are set up prior to the start of the conference and do not change while the conference is in progress. By definition the MLCT mode and bridge state during a conference must be the same, either sender's choice or viewer's choice.

When the conference is first initiated, bridge 103 comes up in the stand alone (SA) condition. In the SA condition bridge 103 operates a conference for just its serving rooms.

When the bridge verifies that all of its broadcast links and MLCT links are active, it assumes the distributed (DS) condition. In the DS condition the bridge will operate in the conference with other MLCTs. The conference messages are exchanged with the other MLCTs. If the MLCT is in the DS condition and one of its broadcast or MLCT links becomes inactive, bridge 103 assumes the SA state again.

If the bridge has communication with the other MLCTs it will notify them of its DS/SA condition transitions by transmitting an MLCT status (MSTAT) message specifying the condition (DS,SA) it has assumed.

The MLCT will try to operate the conference as set up by the commands entered through MS 101. At the initialization of the conference the MLCT mode (VC,SC) and MLCT's own ID is specified before any links are assigned. MS 101 will have already downloaded the program code for the required bridge state into bridge 103. Bridge 103 starts up in the SA condition in the mode specified (VC,SC) with all ports unassigned.

1. MS 101 communicates with bridge 103 to assign a port to a room (MS specifies room ID) or assign a port's in-link, i.e., an incoming transmission path, as a MLCT link (MS specifies MLCT ID) and/or assign the port's out-link, i.e., an outgoing transmission path, as a broadcast link.

2. Bridge 103 marks the in and/or out link as assigned, inactive, and muted.

a. If the port is assigned to a room bridge 103 marks that room assigned.

b. If the in link is assigned to an MLCT bridge 103 marks that MLCT assigned.

3. Bridge 103 trys to establish communication over the links. If communication is established the link is marked active.

4. If decryptor 1002 (FIG. 10) detects no facility failure in the audio signal of the assigned incoming link, bridge 103 unmutes the audio signal and marks the in link as unmuted.

Any subsequent command entered through one of the MLCT's administrative links that declares link(s) to be assigned will be accepted only if it does not reassign links that are presently assigned. All of these subsequent commands are executed (if they are accepted) in the same manner as the first command that assigned links in the conference.

Any subsequent command entered through one of the MLCT's administrative links that declares an in link and/or out link to be unassigned will be accepted only if that in link and/or out link is presently assigned. MS 101 communicates with bridge 103 to update the bridge's link assignments. Bridge 103 does the following:

1. Mark the specified links as unassigned. 2. If any links are being marked unassigned were assigned to rooms, mark those rooms as unassigned. 3. If the last MLCT link assigned to another MLCT, MLCT J, is being marked unassigned, then:

a. MLCT J is marked unassigned.

b. All rooms served by MLCT J are marked unassigned.

Any link or room that is marked unassigned is automatically marked inactive and muted.

While the MLCT is involved in a conference (i.e., some links are assigned), no command entered into the MLCT that specifies changing either the MLCT mode or MLCT's own ID will be accepted.

Broadcast links are dedicated to ensure that the MLCT will be able to transmit any of the required combination of video signals to the other MLCTs. At the time of the conference set-up, the MLCT decides how to dedicate each of its broadcast links. The dedication of these broadcast links will not be changed unless the conference set up is changed.

In a Viewer's Choice conference, MLCTs may need more than one broadcast link. The push-to-see (PTS) mode requires that MLCTs be able to transmit any combination of video signals to the rooms. In a Viewer's Choice conference the broadcast links are dedicated according to the following priorities:

1. If the MLCT has enough broadcast links it assigns a broadcast link to each of its serving rooms. In this case all of the other MLCTs always receive video from every room served by this MLCT.

2. If the MLCT has enough broadcast links it assigns a broadcast link to each of the rooms served by another MLCT. In this case the MLCT will always be able to transmit the video required for each of the rooms served by other MLCTs.

3. If the MLCT does not have enough broadcast links to satisfy either of two previous cases, then the MLCT does not have enough broadcast links to operate properly in the conference. In this case the MLCT prints a warning message.

If the MLCT has more than enough broadcast links needed for dedication to the rooms, then it marks the remaining broadcast links as undedicated.

In a Sender's Choice conference each MLCT requires only one broadcast link. This broadcast link is not dedicated.

Returning to MLCT FIG. 1, there is shown MLCT1 including a microprocessor system (MS) 101, digital cross connect 102, bridge 103 and transmission facility interface 104 which are interconnected as shown by a multiplicity of data and control paths in order to perform required multilocation audio video teleconferencing functions.

Microprocessor System (MS)

The MLCT microprocessor system (MS) 101 is shown in simplified block diagram form in FIG. 4. Shown are CPU 401, memory 402, back-up memory 403, peripheral interface 404 and communications interface 405 all interconnected via bus 406. Memory 402 includes program storage in ROM and data storage in RAM. Back-up memory 403 stores data pertaining to conference set-up in a nonvolatile storage such as bubble memory in order to maintain conference set-up information integrity in the event of a short-time power outage to eliminate the re-entry of the information at the data terminals. Microprocessor system 101 communicates via peripheral interface 404 to transmission facility interface 104, cross connect 102 and bridge 103. Peripheral interface 404 communicates to the transmission facility interface 102 to transfer time-slot map information as discussed hereinafter or in other words to allow a connection to a VTS port of the MLCT. Microprocessor system 101 communicates through peripheral interface 404 to cross-connect 102 to map the time multiplexed switches (TMS) for configuring the TMS output data links 603-1 through 603-N (FIG. 6) to contain the information shown in TABLE 3 below and to perform the video switch function by the use of N.times.N switch 602 (FIG. 6) as described below. The bridge 102 communication is also handled by the peripheral interface 404. Information transfer to bridge 103 includes VTS port assignment, conference set-up including the designation of the various connections to the VTS data links and whether conference rooms or MLCTs are connected to them. Communications interface 405 is used to provide a connection to serial data terminal connections 105-1 through 105-T, in one example T=5, which are used to communicate with the conference set-up operator, a reservation system, or a port system to handle the conference reservation from multiple locations and to perform maintenance operations on the system. The microprocessor system 101 functions may be divided into three distinct classes: maintenance, operational (video switches), and conference parameter management. It performs all communication and administrative functions for the MLCT. It has communication access to all major components of the system to perform conference set-up operations, maintenance functions, error recovery, transmission facility performance monitoring, and video switches upon request from bridge 103. Microprocessor system 101 is essentially identical to the arrangement described by A. J. Cirillo, L. F. Horney II and J. D. Moore in an article entitled, "DACS Microprocessor System", NTC'81, IEEE 1981 National Telecommunications Conference, Vol. 1, pages B1.3.1-B1.3.6, November 1981.

Transmission Facility Interface

Details of transmission facility interface 104 are shown in simplified block diagram form in FIG. 5. It includes VTS ports 500-1 through 500-N, each of which includes a plurality of digroup circuits 501-1 through 501-R. As noted above, in this example two T1 lines are used for each of VTS ports 500-1 through 500-N and, therefore, two digroup circuits are used per VTS port. Again, the VTS ports connect transmission facility interface 104 via transmission facilities 10 (FIG. 1) to associate conference rooms and/or to associated MLCTs. Each of digroup circuits 501-1 through 501-R is connected via a corresponding one of the data links 502-1 through 502-R to cross connect 102. Each of digroup circuits 501-1 through 501-R in a VTS port receives data from cross connection 102 on a shared data link, for example, via data link 108-1. Each digroup circuit in transmission facility interface 102 provides a read-write capability to microprocessor system 101 of all error source registers (not shown) and control registers (not shown). The error source registers relate to various internal hardware error detectors as well as to transmission facility related problems such as T1 framing errors, out-of-frame conditions, slips and carrier failure alarms (CFA). In addition to the DS-1 termination function, the digroup circuit implements the "time" portion of the time-space-time switching function of the MLCT. Its receiving section contains a line clock recovery circuit, a framer for recovery of the Ft framing bits, an elastic store, transmission facility error detectors and a time-slot interchanger (RTSI) (all not shown) to transform the T1 frame format to one compatible with that of the cross-connect, i.e., the cross connect data format of FIG. 3. Its transmitting section contains a second time-slot interchanger (TTSI) (not shown) and a DS-1 signal formatter (not shown) to convert the cross-connect data format to the DS-1 format.

The signal format provided by the digroup circuit to the cross-connect 102 is shown in FIG. 3. It consists of a frame of 256 time-slots, labeled time-slot 0 through time-slot 255. It is transported by three rails at a data rate of 8.192 Mb/sec each. Each time-slot contains 12 bits of information: 8 data bits, labeled D1 through D8, three spare bits, and a parity bit that provides odd parity over the 12 bits in the time slot and the eight-bit code representing the time-slot number. The RTSI may be configured to fill any of the 256 time slots with the received 24 words of the incoming T1 line. Similarly, the TTSI may choose any of the 256 time-slots (up to 24) and selectively place them in the outgoing T1 line.

In this example, the digroup circuits 502-1 through 502-R, where R=4, for VTS port 500-1 identify and format the incoming DS-1 signals. Specifically, digroup circuit 502-1 identifies the video control signals, c bit and audio signals in words 1, 2 and 3 and formats them in time slots 0, 1 and 2 in the cross connect frame format of FIG. 3. Similarly, it identifies the video information in words 4 through 24 and formats it into time slots 64 through 84 in the cross connect frame format of FIG. 3. Digroup circuit 502-2 identifies the video information in signal DS1 No. 2 and formats it into time slots 85 through 108 of the cross connect frame format. Digroup circuit 502-3, if used, identifies the video information in signal DS1 No. 3 and formats it into time slots 108 through 132 of the cross connect format. Finally, digroup circuit 502-4, if used, identifies the video information in signal DS1 No. 4 and formats it into time slots 133 through 156 of the cross connect format. For VTS port 500-2 the only difference from VTS port 500-1 is in the formatting of the video control signal, c-bit and audio signals. In this example, this information is formatted into time slots 4, 5 and 6 of the cross connect frame format.

This formatting is shown in FIG. 9 relating to the cross connect 102 frame formats. There is shown that for VTS port 500-3 the video control, c-bit and audio information is in time slots 8, 9 and 10, for VTS port 500-4 in time slots 12, 13 and 14, for VTS ports 500-4 in time slots 16, 17 and 18 and for VTS port 6, i.e., N=6, in time slots 20, 21 and 22. These formatted signals are supplied to cross connect 102.

Such digroup circuits are known in the art, see for example the digroup circuit described by R. P. Abbott and D. C. Koehler in an article entitled, "Digital Access and Cross-Connect System--System Architecture", NTC'81, IEEE 1981 National Telecommunication Conference, Vol. 1, pages B1.2.1-B1.2.7 at page B1.2.2., November 1981.

VTS ports 500 can be assigned in a conference as follows:

1. Both the input and output data links of a VTS port are assigned to a room;

2. The output data link of the VTS port is assigned as a so-called broadcast link, i.e., the outgoing signal is supplied to all other MLCTs in the conference; and

3. The input data link of the VTS port is assigned as a MLCT link, i.e., it receives an outgoing broadcast signal from another MLCT.

Cross Connect

Details of cross-connect 102 are shown in simplified block diagram form in FIG. 6. Cross-connect 102 provides the space switching function of the MLCT time-space-time switching function. Cross-connect 102 includes time-multiplexed switches (TMS) 601-1 through 601-N and N.times.N switch 602. Time multiplexed switches 601-1 through 601-N are assigned on a one-to-one basis to VTS ports 500-1 through 500-N, respectively, in transmission facility interface 104. Data links 107-1 through 107-N are supplied from transmission interface 104 to TMS 601-1 through 601-N, respectively. Also supplied to TMS 601-1 through 601-N are data links 109-1 through 109-N, respectively. Data links 109-1 through 109-N carry processed information from bridge 103 relating to associated VTS ports 500-1 through 500-N, respectively. Each of TMS 601-1 through TMS 601-N selects on a per time slot basis information from its input data links and combines the information to generate at its output data link another 256 time-slot composite signal frame containing the time slot selection that the TMS is programmed to produce. It is important to note that the video information from a conference location is included in several incoming signals and that the TMS combines the information into the one composite signal. This combining of all the video information from a corresponding conference location into one composite signal enables, in accordance with an aspect of the invention, a rapid switch of the video being viewed. Outputs from TMS 601-1 through 601-N are controllably selected by N.times.N switch 602 and supplied via 108-1 through 108-N, respectively, to transmission facility interface 104 for transmission on T1 transmission facilities to transmission facility 10 to be routed to appropriate ones of the conference room and/or other MLCTs, TMS 601-1 through TMS 601-N and N.times.N switch 602 are controlled by microprocessor system 101 to realize a desired video and audio switch to the ports. Through this arrangement anyone of the composite signals from TMS 601-1 through TMS 601-N is selectable via switch 602 for transmission to any one of VTS ports 500.

It is noted that each VTS port receives an audio mix from all the other ports. Thus, the audio that must accompany the video to each port is a different mix. The appropriate audio mix and video are switched to the VTS ports by employing cross-connect 102. Error free, i.e., non-disruptive switching is realized, in accordance with an aspect of the invention, by employing TMS 601-1 through 601-N to each generate a so-called composite audio and video signal. The composite signal includes all the video information from a room associated with the corresponding VTS port and the audio mixes generated by bridge 103 to be transmitted to all of the rooms and partial audio sums to be transmitted to other MLCTs. Cross connect 102 time slot assignments of the signals generated at the outputs of TMS 601-1 through 601-N are shown in FIG. 9. Accordingly, shown in FIG. 9 are the composite signals combined in cross-connect 102 for each of the VTS ports 500-1 through 500-N. Thus, for VTS port 500-1 the audio mix to VTS port 1 is in fixed time slots 32, 33 and 34 as supplied from bridge output circuit 1005, the audio mix to VITS port 500-2 is in fixed time slots 36, 37 and 38, the audio mix to VTS port 500-3 is inserted into fixed time slots 40, 41 and 42, the audio mix to VTS port 500-9 is in fixed time-slots 44, 45 and 46, the audio mix to VTS port 500-5 is in fixed time slots 48, 49 and, 50 and finally, the audio mix to VTS port 500-6 is in time slots 52, 53 and 54. The video from VTS port 500-1 is combined into time slots 64 through 156. The audio from VTS port 500-1 which is in time slots 0, 1 and 2 is supplied to bridge 103 via 110-1 to be appropriately mixed with the audio from the other VTS ports and, then, supplied via 109-1 from bridge 103 to TMS 601-1 in the appropriate fixed time slots in the composite signals associated with VTS port 500-1. The composite signals associated with VTS ports 500-2 through 500-6 are similarly obtained as shown in FIG. 9. Consequently, when the video from anyone of the VTS ports and, hence, the associated conference room is switched via N.times.N switch 602 to anyone of the other conference rooms, the proper audio mix for the specific conference rooms is present and obtained by the MLCT selecting the audio mix in the fixed time slots assigned to the associated conference rooms. The functions of TMS 600 and switch 602 may be realized by employing dual multiplexers of a type described in the article entitled, "Digital Access and Cross-Connect System-System Architecture" noted above.

FIG. 7 shows in simplified block diagram form details of time multiplexed switches 601 of cross-connect 102 (FIG. 6). Accordingly, shown are (R+1).times.1 data selector 701, TMS control memory 702 and time slot counter 703. Selector 701 is controlled by control codes stored in control memory 702. The control codes are written into memory 702 from microprocessor system 101 and include the time slot switching information for the time multiplexed switch for an assigned VTS port. Once the control information is written into control memory 702 no further interaction with microprocessor system 101 is required until a new data link selection is made. Control memory 702 is addressed by time slot counter 703 which generates a sequentially incrementing modulo-256 counter signal synchronized to the time slot occurrences of the cross-connect data format as shown in FIG. 3.

FIG. 8 shows in simplified block diagram form details of N.times.N switch 602 of cross-connect 102 FIG. 6. Switch 602 includes N.times.1 data selectors 801-1 through 801-N which are controlled by control registers 802-1 through 802-N, respectively. Each of outputs 108-1 through 108-N of data selectors 801-1 through 801-N, respectively, is connected to an associated one of VTS ports 500-1 through 500-N (FIG. 5). Outputs 603-1 through 603-N from time multiplexed switches 601-1 through 601-N (FIG. 6), respectively, are supplied to respective inputs of selectors 801-1 through 801-N. Switching commands are supplied from microprocessor system 101 via control lines 605-1 through 605-N to control registers 802-1 through 802-N, respectively. In response to the switching commands each of selectors 801-1 through 801-N selects an appropriate one to its inputs and provides it to its associated VTS port in transmission facility interface 104. Consequently, any one of the composite signals supplied from time multiplexed switches 601 can be selected for transmission to any one of the VTS ports 500. The input selection is controlled to occur at the boundary between the cross-connect data format frame in order to prevent any mixing of information from different inputs within a given frame.

In summary, the operation of cross-connect 102 in realizing nondisruptive audio and rapid video switching, in accordance with an aspect of the invention, is such that the first 3 words of DS-1 No. 1 of all N incoming VTS signals are identified by and formatted into predetermined time slots by digroups circuit 501 and sent via TMS 601-1 through 601-N to bridge 103 for processing the audio and control information and for performing sub-byte bit manipulation of video-related signaling bits located in the first word. All other words containing video information are formatted into a composite video signal and provided to N.times.N switch 602 for the video switching function of the MLCT along with processed audio, control, and video related information are supplied by each of data links 109-1 through 109-N from bridge 103. After any selection is made by N.times.N switch 602, it is up to the particular one of digroup circuits 501 (FIG. 5) to choose the necessary timeslots to form the corresponding outgoing VTS signal.

This implies, as will be seen in the following, that the processed audio and control signals generated in bridge 103 must appear on all data links 603 presented to N.times.N switch 602 in order to affect only video information when the switch state is changed. The time-slot assignment has been chosen, along with other system features, so that after a conference configuration has been decided and set-up, the time-space-time switching configuration is static except for N.times.N switch 602. N.times.N switch 602 is the only switching element whose configuration is dynamic, i.e., during video switches. The other switching elements remain constant until a new conference configuration is required, i.e., addition or deletion of a conference room or MLCT. This type of arrangement allows, in accordance with an aspect of the invention, very efficient and rapid video selection operations. In fact, not using the above method implies remapping one time-slot at a time of all the switching elements to perform a video switch thereby resulting in serious video selection speed degradations.

Table 1 shows the relative time-slot assignment of all information groups as they appear at the output of TMS 601-1 through 601-N. Entries of the form "vnwn" and "vnWn" represents a group of 3 timeslot each. The "Vn" entries represent a group of 21+(24.times.R) time-slots to accommodate the video information from each VTS port. The table is subdivided into two sections each pertaining to where the information is routed. Bridge 103, for example, has access in space and time to all audio and control inputs to the MLCT. Conversely, bridge 103 provides N copies of the processed audio and control information mixed with video portions pertinent to each VTS port. The transmit sections of digroup circuits (DC) 500 in the transmission facility interface 104 (FIG. 4) choose the time-slots under the "VTS Output Contribution" to construct the word pattern in the R outgoing T1 lines. Once this selection is performed, no other interaction is done with the DC TTSI. When a "space" switch is performed by N.times.N switch 602 (FIG. 6) it represents a vertical movement of the "VTS Output Contribution" section of the time-slot assignment table which affects only video information.

                                      TABLE 1
    __________________________________________________________________________
    Cross-Connect Time-Slot Assignment
    Time-Slot Assignment
    VTS Input Contribution Bridge 103 Contribution
    To Bridge 103       VTS Output Contribution
    __________________________________________________________________________
    L 1 v1w1
            --  --  --  v1 v1W1
                               v1W2
                                   V1Wn
                                       v1WN
    I 2 --  v2W2
                --  --  V2 v2W1
                               v2W2
                                   v2Wn
                                       v2WN
    N n --  --  vnwn
                    --  Vn vnW1
                               vnW2
                                   vnWn
                                       vnWN
    K N --  --  --  vNwN
                        VN vNW1
                               vNW2
                                   vNWn
                                       vNWN
    __________________________________________________________________________
     LEGENDA
     vn Video in word 1 of DS1 No. 1 from VTS Input Port n
     Vn Video from VTS Input Port n
     wn Control and Audio from VTS Input Port n
     Wn Control and Bridged Audio to VTS Output Port n
     -- Unassigned TimeSlot Group

                  TABLE 2
    ______________________________________
    VTS Data Format: Audio Group
    A-bit      Mu-law    Description
    ______________________________________
    A1     A9      M0        Mantissa Least Significant Bit
    A2     A10     M1
    A3     A11     M2
    A4     A12     M3        Mantissa Most Significant Bit
    A5     A13     L0        Cord Least Significant Bit
    A6     A14     L1
    A7     A15     L2        Cord Most Significant Bit
    A8     A16     S         Sign
    ______________________________________

                  TABLE 3
    ______________________________________
    VTS Data Format: Audio Decipherment Group
    ______________________________________
    Odd Numbered D-bits
    n   Counter Contents  Check Bits
    ______________________________________
    0   L1      L2     L3    L4   R1    R2    R3   R4
    1   L5      L6     L7    L8   R5    R6    R7   R8
    2   L9      L10    L11   L12  R9    R10   R11  R12
    3   L13     L14    L15   L16  R13   R14   R15  R16
    4   L17     L18    L19   L20  R17   R18   R19  R20
    5   L21     L22    L23   L24  R21   R22   R23  R24
    6   L25     L26    L27   L28  R25   R26   R27  R28
    7   L29     L30    L31   L32  R29   R30   R31  R32
    R4n+1 = L4n+1 .sym. L4n+2 .sym. L4n+3
    R4n+2 = L4n+2 .sym. L4n+3 .sym. L4n+4
    R4n+3 = L4n+1 .sym. L4n+2 .sym. L4n+4
    R4n+4 = L4n+1 .sym. L4n+3 .sym. L4n+4
    ______________________________________
    Even Numbered D-bits
    n    S1      S2     S3    S4   S5    S6   P    FAn
    ______________________________________
    0    1       0      0     1    1    1     P    0
    1    1       0      0     1    1    1     P    0
    2    1       0      0     1    1    1     P    0
    3    1       0      0     1    1    1     P    0
    4    1       0      0     1    1    1     P    1
    5    1       0      0     1    1    1     P    1
    6    1       0      0     1    1    1     P    1
    7    1       0      0     1    1    1     P    1
    ______________________________________
     The symbol .sym. indicates an "Exclusive OR" function.

                                      TABLE 4
    __________________________________________________________________________
                 Received
                 Counter   Counter
                                 Cipher Byte
                                           Flow
       D-bit K   Contents  Encryption
                                 Selection to
                                           Chart
    K  Processing
                 Bookkeeping
                           Request
                                 Decrypt Audio
                                           Node
    __________________________________________________________________________
    001
       RTMPO=D=L1          ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (1,[Ct]1)
    002
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    003
       LRTMP1=D=L2               CTADDR=*[Ct2]0
                                           LR
    004
       FRAMING=D+1               CTADDR=*[Ct3]0
                                           S
    005
       LRTMP2=D=L3         ENCRQ CTADDR=*[Ct0]1
                                           LR
                           (2,[Ct]0)
    006
       FRAMING=D+1               CTADDR=*[Ct1]1
                                           S
    007
       LRTMP3=D=L4               CTADDR=*[Ct2]1
                                           LR
    008
       FRAMING=D+0               CTADDR=*[Ct3]1
                                           S
    009
       LRTMP4=D=R1         ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (3,[Ct]1)
    010
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    011
       LRTMP5=D=R2               CTADDR=*[Ct2]0
                                           LR
    012
       FRAMING=D+0               CTADDR=*[Ct3]0
                                           S
    013
       LRTMP6=D=R3
                 NXTPT0 =  ENCRQ CTADDR=*[Ct0]1
                                           LR
                 HAM(LRTMP)
                           (4,[Ct]0)
    014
       PARITY=D                  CTADDR=*[Ct1]1
                                           P
    015                          CTADDR=*[Ct2]1
                                           LR
    016
       FRAMING=D+1               CTADDR=*[Ct3]1
                                           S
    017
       LRTMPO=D=L5         ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (5,[Ct]1)
    018
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    019
       LRTMP1=D=L6               CTADDR=*[Ct2]0
                                           LR
    020
       FRAMING=D+1               CTADDR=*[Ct3]0
                                           S
    021
       LRTMP2=D=L7         ENCRQ CTADDR=*[Ct0]1
                                           LR
                           (6,[Ct]0)
    022
       FRAMING=D+1               CTADDR=*[Ct1]1
                                           S
    023
       LRTMP3=D=L8               CTADDR=*[Ct2]1
                                           LR
    024
       FRAMING=D+0               CTADDR=*[Ct3]1
                                           S
    025
       LRTMP4=D=R5         ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (7,[Ct]1)
    026
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    027
       LRTMP5=D=R6               CTADDR=*[Ct2]0
                                           LR
    028
       FRAMING=D+0               CTADDR=*[Ct3]0
                                           S
    029
       LRTMP6=D=R7
                 NXTPT1 =  ENCRQ CTADDR=*[Ct0]1
                                           LR
                 HAM (LRTMP)
                           (8,[Ct]0)
    030
       PARITY=D                  CTADDR=*[Ct1]1
                                           P
    031                          CTADDR=*[Ct2]1
                                           LR
    032
       FRAMING=D+1               CTADDR=*[Ct3]1
                                           S
    033
       LRTMPO=D=L9         ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (9,[Ct]1)
    034
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    035
       LRTMP1=D=L10              CTADDR=*[Ct2]0
                                           LR
    036
       FRAMING=D+1               CTADDR=*[Ct3]0
                                           S
    037
       LRTMP2=D=L11        ENCRQ CTADDR=*[Ct0]1
                                           LR
                           (10,[Ct]0)
    038
       FRAMING=D+1               CTADDR=*[Ct1]1
                                           S
    039
       LRTMP3=D=L12              CTADDR=*[Ct2]1
                                           LR
    040
       FRAMING=D+0               CTADDR=*[Ct3]1
                                           S
    041
       LRTMP4=D=R9         ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (11,[Ct]1)
    042
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    043
       LRTMP5=D=R10              CTADDR=*[Ct2]0
                                           LR
    044
       FRAMING=D+0               CTADDR=*[Ct3]0
                                           S
    045
       LRTMP6=D=R11
                 NXTPT2 =  ENCRQ CTADDR=*[Ct0]1
                                           LR
                 HAM(LRTMP)
                           (12,[Ct]0)
    046
       PARITY=D                  CTADDR=*[Ct1]1
                                           P
    047                          CTADDR=*[Ct2]1
                                           LR
    048
       FRAMING=D+1               CTADDR=*[Ct3]1
                                           S
    049
       LRTMPO=D=L13        ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (13,[Ct]1)
    050
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    051
       LRTMP1=D=L14              CTADDR=*[Ct2]0
                                           LR
    052
       FRAMING=D+1               CTADDR=*[Ct3]0
                                           S
    053
       LRTMP2=D=L15        ENCRQ CTADDR=*[Ct0]1
                                           LR
                           (14,[Ct]0)
    054
       FRAMING=D+1               CTADDR=*[Ct1]1
                                           S
    055
       LRTMP3=D=L16              CTADDR=*[Ct2]1
                                           LR
    056
       FRAMING=D+0               CTADDR=*[Ct3]1
                                           S
    057
       LRTMP4=D=R13        ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (15,[Ct]1)
    058
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    059
       LRTMP5=D=R14              CTADDR=*[Ct2]0
                                           LR
    060
       FRAMING=D+0               CTADDR=*[Ct3]0
                                           S
    061
       LRTMP6=D=R15
                 NXTPT3 =  ENCRQ CTADDR=*[Ct0]1
                                           LR
                 HAM(LRTMP)
                           (16,[Ct]0)
    062
       PARITY=D                  CTADDR=*[Ct1]1
                                           P
    063                          CTADDR=*[Ct1]1
                                           LR
    064
       FRAMING=D+1               CTADDR=*[Ct3]1
                                           S
    065
       LRTMPO=D=L17        ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (17,[Ct]1)
    066
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    067
       LRIMP1=D=L18              CTADDR=*[Ct2]0
                                           LR
    068
       FRAMING=D+1               CTADDR=*[Ct3]0
                                           S
    069
       LRTMP2=D=L19        ENCRQ CTADDR=*[Ct0]1
                                           LR
                           (18,[Ct]0)
    070
       FRAMING=D+1               CTADDR=*[Ct1]1
                                           S
    071
       LRTMP3=D=L20              CTADDR=*[Ct2]1
                                           LR
    072
       FRAMING=D+0               CTADDR=*[Ct3]1
                                           S
    073
       LRTMP4=D=R17        ENCRQ CTADDR=*[Ct0]0
                                           LR



                           (19,[Ct]1)
    074
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    075
       LRTMP5=D=R18              CTADDR=*[Ct2]0
                                           LR
    076
       FRAMING=D+0               CTADDR=*[Ct3]0
                                           S
    077
       LRTMP6=D=R19
                 NXTPT4 =  ENCRQ CTADDR= *[Ct0]1
                                           LR
                 HAM(LRTMP)
                           (20,[Ct]0)
    078
       PARITY=D                  CTADDR=*[Ct1]1
                                           P
    079                          CTADDR=*[Ct2]1
                                           LR
    080
       FRAMING=D+1               CTADDR=*[Ct3]1
                                           S
    081
       LRTMPO=D=L21        ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (21,[Ct]1)
    082
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    083
       LRTMP1=D=L22              CTADDR=*[Ct2]0
                                           LR
    084
       FRAMING=D+1               CTADDR=*[Ct3]0
                                           S
    085
       LRTMP2=D=L23        ENCRQ CTADDR=*[Ct0]1
                                           LR
                           (22,[Ct]0)
    086
       FRAMING=D+1               CTADDR=*[Ct1]1
                                           S
    087
       LRTMP3=D=L24              CTADDR=*[Ct2]1
                                           LR
    088
       FRAMING=D+0               CTADDR=*[Ct3]1
                                           S
    089
       LRTMP4=D=R21        ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (23,[Ct]1)
    090
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    091
       LRTMP5=D=R22              CTADDR=*[Ct2]0
                                           LR
    092
       FRAMING=D+0               CTADDR=*[Ct3]0
                                           S
    093
       LRTMP6=D=R23
                 NXTPT5 =  ENCRQ CTADDR=*[ Ct0]1
                                           LR
                 HAM(LRTMP)
                           (24,[Ct]0)
    094
       PARITY=D                  CTADDR=*[Ct1]1
                                           P
    095                          CTADDR=*[Ct2]1
                                           LR
    096
       FRAMING=D+1               CTADDR=*[Ct3]1
                                           S
    097
       LRTMPO=D=L25        ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (25,[Ct]1)
    098
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    099
       LRTMP1=D=L26              CTADDR=*[Ct2]0
                                           LR
    100
       FRAMING=D+1               CTADDR=*[Ct3]0
                                           S
    101
       LRTMP2=D=L27        ENCRQ CTADDR=*[Ct0]1
                                           LR
                           (26,[Ct]0)
    102
       FRAMING=D+1               CTADDR=*[Ct1]1
                                           S
    103
       LRTMP3=D=L28              CTADDR=*[Ct2]1
                                           LR
    104
       FRAMING=D+0               CTADDR=*[Ct3]1
                                           S
    105
       LRTMP4=D=R25        ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (27,[Ct]1)
    106
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    107
       LRTMP5=D=R26              CTADDR=*[Ct2]0
                                           LR
    108
       FRAMING=D+0               CTADDR=*[Ct3]0
                                           S
    109
       LRTMP6=D=R23
                 NXTPT6 =  ENCRQ CTADDR=*[Ct0] 1
                                           LR
                 HAM(LRTMP)
                           (28,[Ct]0)
    110
       PARITY=D                  CTADDR=*[Ct1]1
                                           P
    111                          CTADDR=*[Ct2]1
                                           LR
    112
       FRAMING=D+1               CTADDR=*[Ct3]1
                                           S
    113
       LRTMPO=D=L29        ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (29,[Ct]1)
    114
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    115
       LRTMP1=D=L30              CTADDR=*[Ct2]0
                                           LR
    116
       FRAMING=D+1               CTADDR=*[Ct3]0
                                           S
    117
       LRTMP2=D=L31        ENCRQ CTADDR=*[Ct0]1
                                           LR
                           (30,[Ct]0)
    118
       FRAMING=D+1               CTADDR=*[Ct1]1
                                           S
    119
       LRTMP3=D=L32              CTADDR=*[Ct2]1
                                           LR
    120
       FRAMING=D+0               CTADDR=*[Ct3]1
                                           S
    121
       LRTMP4=D=R29        ENCRQ CTADDR=*[Ct0]0
                                           LR
                           (31,[Ct]1)
    122
       FRAMING=D+0               CTADDR=*[Ct1]0
                                           S
    123
       LRTMP5=D=R30              CTADDR=*[Ct2]0
                                           LR
    124
       FRAMING=D+0               CTADDR=*[Ct3]0
                                           S
    125
       LRTMP6=D=R31
                 NXTPT6 =  ENCRQ CTADDR=*[Ct0]1
                                           LR
                 HAM(LRTMP)
                           (0,[Ct]0)
                 PRSPT=NXTPT
    126
       PARITY=D                  CTADDR=*[Ct1]1
                                           P
    127                          CTADDR=*[Ct2]1
                                           LR
    128
       FRAMING=D+1               CTADDR=*[Ct3]1
                                           S
    __________________________________________________________________________