Configuring Call Transfers and Conferencing

A number of parameters needs to be configured before your Modem or Telephony Card (eg. Dialogic) can correctly transfer and conference calls.

The most important parameters are the signals which your PBX or Telephone Network uses to place calls on hold and to forward or conference calls. If you do not know what those signals are, you will probably need to ask your PBX supplier or call your Telephone Company.

On almost all systems the “hookflash” (also known as “flash”) signal is used in one way or another. The length of the hookflash required differs from system to system - the length used by your Modem or Telephony Card will have to match that required by your PBX / Telephone Network, otherwise the transfers/conferences will not work.

Most modems cannot vary the length of their hookflash, and if their default length does not match the length required by your PBX / Telephone Network then you will not be able to use that modem to transfer/conference calls.

Telephony Cards allow the hookflash length to be set by the user – ensuring that a Telephony Card can be configured to allow it to successfully perform call transfers and conferencing. This is why it is highly recommended to use a Telephony Card if your application needs to do call transfers / conferencing.

The signals sent to your PBX or Telephone Network can be configured in the TSP configuration dialog. The voice board will generate the specified signals to command the PBX / Telephone Network to perform call transfers and conferences when relevant functions are called.

The "!" character represents a hookflash.

Setting Hookflash length on Dialogic cards

Win98/NT: Open Control Panel’s Telephony applet, select the Telephony Drivers tab, select the Dialogic Service Provider and the press Configure.

Win2000/XP: Open Control Panel’s “Phone and Modem Options” applet, select the Advanced tab, select the Dialogic Service Provider and then click Configure.

A Dialogic TSP Configuration window should appear:

Press Advanced to show the Configuration Service window:

The Hookflash time can be set in the Flash Time text box. The default value of 50 represents a hookflash time of half a second. Many systems require a value lower then that - around 100 or 200 milliseconds - requiring a value of 10 or 20 specified in the Flash Time text box respectively.

Note: Any changes made in the Dialogic’s Configuration Service window will not take effect until the Dialogic System Service is restarted. If you don’t know how to do this then just restart the computer.

Sometimes the flash time set here may not work. You can do as following:

1. Select “Australia/NZ” as the Country in the DCM (Dialogic Configuration manager).

2: Keeping “Australia/NZ” selected as the Country go to Dialogic’s DATA subdirectory (usually in C:\Program Files\Dialogic\DATA) and edit the file An_d4p.prm using Wordpad. You will need to change the line:

# PARAM 52:(DECIMAL WORD) 50 # Hook Flash/earth recall duration

to:

PARAM 52:(DECIMAL WORD) 10 # Hook Flash/earth recall duration

Ie: remove the # at the beginning and change 50 to 10 – parameter is in 10ms units, so a setting of 10 will indicate 100ms.

Configuring Dialogic controlled call transfers

The PBX signals are then configured using the Dialogics’s TAPI service configuration panel:

In this dialog, three PBX strings are very important to perform transfer function. They are Transfer, Complete Conference and Drop.

Transfer string is used to make a hook-flash before dialing the transfer number.

Complete Conference string is used to complete the transfer as a conference after the consultaion call has been answered. Here, with PBX of China Telecom, we set !,3.

The five Drop strings at the right of dialog is used to drop the consultacion call in different status including Proceding,Connected, Disconnected, RingBack, Busy and retrieve the original call. We use "!,1" to do this with PBX of China Telecom. If they are not set, you will not be able to retrieve the original if the consultation call is not answered or the extention is busy, or they drop the call immediately after answering. For a stable caller center with call transfer function, that is unacceptable.

Corresponding to the PBX string, we do the transfer with three phones and the PBX of China Telecom like this.

1 A and B are in a connected call.

2. Phone:B make a hook-flash on the phone(many phone have a R key to do this), and dial the number of C.

Thus the consultation call to C to made by B.

3.There are several cases after the consultation has been made:

1.C hear rings and answered the consultation call.
In this case, B usually press !,3 to complete the transfer as a conference call or press !,1 to drop the consultation call and retrieve the original call. (Drop consultation call in Connected state)
2.C's phone is busy
B has to press "!,1" to drop the consultation call and retrieve the original call. (Drop consultation call in Busy state)
3. C does not answer the call
B has to press "!,1" to drop the consultation call and retrieve the original call. (Drop consultation call in Proceding state)
4. C answered the call, but then immediately drop the call.
B has to press "!,1" to drop the consultation call and retrieve the original call. (Drop consultation call in Disconnected state)

This is quite straight foward with three phones and PBX. But with dialogic card, it has a slightly difference.

With dialogic card, & is default string to send to the PBX when it make a drop. But when aborting a transfering, that do not work. So strings for drop at different state should be set.

The screen above shows the basic configuration which should work for many PBX systems. You will need to consult your PBX or telephone system support staff to determine the appropriate settings for your system. 

Further help on configuring the Dialogic settings can be found in the Dialogic help file.

Note: Any changes made in the Dialogic’s Configuration Service window will not take effect until the Dialogic System Service is restarted. If you don’t know how to do this then just restart the computer.

The examples above show configuration screens used by the Dialogic's TAPI driver. When using CT Media please consult the CT Media manuals for instructions on setting these corresponding parameters under CT Media.