Revision as of 11:10, 8 August 2007

Open Duplex Conference

An open duplex conference in principle an ordinary conversation with more than two participants. An open duplex conference can have a maximum of 4 participants, all using either handset or headset. 20 open duplex conferences can be configured. One station can leave the conference by hanging up. A conference participant can drop out of the conference temporarily to add another station by dialing 56 + directory number. It is possible to control conference set-up remotely. One station can force up to 4 other stations into a conference. Stations can also be forced out of a conference. A telephone call can be included in the conference.

A master station for the conference can be defined. This has the effect that when the master leaves the conference, the whole conference is terminated.

Functional description

Basic feature

A duplex conference in AlphaCom can have maximum 4 participants.

There are 20 numbered conferences, with directory numbers 8301 to 8320. The number of simultaneous active conferences depends on the resources installed in the exchange. Resources used by the conference are allocated from pools at the time a participant enters a conference.

It is also possible to convert an ordinary two-part conversation to a duplex conversation (new in AMC 10.00). This is actually a “transfer to conference”. The last 5 of the 20 conferences are used for such “ad-hoc” conferences.

Participants in a duplex conference are busy (must disconnect before receiving a conversation). A participant leaves the conference by normal disconnection (C-key or replacing handset).

The core of the duplex conference is audio mixing. Each participant speaker gets the audio mix of the microphone signals from the other participants. This is called a conference bridge.

A station with handset lifted is connected directly to the conference bridge in open(full) duplex. (Same applies if the station is marked as having Acoustic Echo Cancelling).

A station in loudspeaking “handsfree” mode is connected to the conference bridge via a vox-duplex connection. (New in AMC 10.00, earlier versions only supported open duplex with lifted handset).

The duplex conference can have a mix of participants connected in open duplex and vox-duplex. (New in AMC 10.00).

New in AMC 10.00: Stations connected in slave modules can also join a duplex conference. Conferences may have 4 priorities. Conferences with higher priority may snatch resources from lower priority functions. The highest priority override the single subscribers priority in situations like conversation, absent state etc.

Joining and leaving conference

Direct entry

Direct entry to a specific conference: Dial the conference number (83xx).

Transfer from conversation to “ad-hoc” conference (new in AMC 10.00)

Transfer from a two-part conversation: Dial “56” during conversation. An unused “ad-hoc” conference is allocated, and the two stations are transferred to the new conference.

In case of an inquiry call from a parked conversation, all three stations will be transferred to a “ad-hoc” conference. Both ends of the open conversation can initiate the transfer by dialling “56”. This is probably the most natural way to establish a conference.

Care has been taken to ensure that also PNCI calls can be transferred to a ad-hoc conference. (no disconnection message during the transfer)

Direct inclusion from within conference

Expand a conference: A participant in a duplex conference can include other stations into the conference: Dial

56 < station number>

or

56 <group number>

The dialler immediately goes back to the conference after terminating the dialling.

This is a “raw” setup function. Transfer and absence status of the target stations are ignored.

Inclusion by inquiry call form conference (new in AMC 10.00)

Expand a conference: A participant in a duplex conference can also make an inquiry call to a station, and ask if somebody there want to join. If yes, dial “56” to transfer the inquired station to the conference. The dialling station returns to the conference as well.

If the inquiry was unsuccessful, just pres C, and the dialler returns to the conference.

In summary:

2 < station number> 56

With the inquiry method, transfer, private and absence status of the target station is followed.

Remote setup from station

Dial from Idle:

74 < station dirno> <conference dirno>

or

75 < group number> <conference dirno>

(Requires appropriate ClassOfService privileges.)

Remote disconnection from station

This feature disconnects specified stations from a duplex conference. Dial from idle:

74 < participant dirno> 8300

or

75 < group number> 8300

This is not a “conference disconnect” function. If the conference has additional members, these will remain in the conference.

Data Protocol messages

Two different messages for forcing stations into a conference:

Dedicated message: $odc, $O_DUPL_CONF, m006F:

$odc <station-or-group> <conference> [<mode>]

Null value or directory number for “duplex conference off” disconnects the subscriber or group from the conference.

(<mode> = 2 means “toggle”).

Response is “COMMAND_RESPONSE” or ILLEGAL_PARAM.

New in AMC 10:00: General call message: $call; m0008:

$call <station> <conference> [<setup-flags>]

The response is COMMAND_RESPONSE. But the response is only transmitted if bit one (“RETURN_ACK”) in the setup-flags is set (append “w1” to the message).

$call also support inclusion of station into a conference in another exchange over AlphaNet.

Identifying a conference:

The entity class ECL_O_DUPL_CONF = 15 is defined for duplex conferences, letter “f” in the “simple linklayer”. So you don’t want to depend on directory numbers, you can send:

$call N3 NF5

is the equivalent of

$call L103 L8305

Common for setup functions

For all remote setup variants it applies that a busy subscriber can not be included in the conference if not the conference has the highest priority to force the subscriber idle.

Group setup variants are still limited to 4 group members. If the number of members in the group exceeds the max number of participants in the conference, the first members of the group that are free are included in the conference.

If a group member is busy with high enough priority, he is skipped and the next group member is involved.

Programming options for conference

These options can be set for each duplex conference:

Master member

Per conference one “master” station can be programmed. The semantics is that when the conference master station leaves the conference, the whole conference is taken down.

(The conference master is not automatically included in the conference. The conference disconnect function only applies if the conference master is included in the conference in the first place.)

Priority

The conference priority controls the priority of resource allocations.

If set to the highest (alarm) priority, the conference can snatch resources from other stations/functions. Busy stations will also be disconnected from normal priority functions in order to be included in alarm-priority conference.

Nitty-gritty details

If in vox-duplex, lift the handset, the station will go to open duplex (wox-duplex resources are released).

If in open-duplex with handset lifted: replace handset while M-key is pressed, will go to vox duplex, provided wox-duplex resources avaliable.

If open duplex mixer allocation succeeded, but no duplex resources was available, the station starts ringing, and you can enter in open duplex by lifing handset.

If the ”dupl_conf_no_vox” nvram-flag is set: Vox duplex is not allowed. When a station is included into a duplex conference, it will start to ring, and the handset has to be lifted in order to connect to the conference audio. If the handset was lifted in the first place, the station is connected to the conference audio directly. The timeout on the ringing is default 30 seconds, the duration is controlled by the same programming as normal private ringing.

Limitations

The conference does not survive an exchange reset.

Participants in slave modules are only supported for multimodules using AGA boards for interconnection (no support for IP voice interconnection)

Installation and technical details

AGA board and programming

The duplex conference requires proper installation of an AGA board.

All audio mixing takes place in the Master module. At least one AGA board is needed, and some AGA resources must be programmed to “2 Open Duplex Conf Mixer” in the “Board” programming. (Each “port” defined in AlphaPro makes two mixer circuits, each 1/16th of AGA).

Other NVRAM programming