4.5. Configuring DTMF Handling

When using Global Call with a DM3 board that uses an embedded stack, by default, DTMF digits are automatically transferred from the IP network to the CT Bus and vice versa. However, the behavior can be configured by setting the value of the PrmDTMFXferMode parameter in the .config file.

When the PrmDTMFXferMode parameter is set to a value of 2 (default), out-of-band (OOB) DTMF transfer is enabled and the following behavior applies:

• DTMF digits from the CT Bus are sent out-of-band to the IP network.
• H.245 UII messages are used to generate DTMF digits which are sent to the CT Bus.
• In-band DTMF digits are set to the CT Bus. In this case, audio from the IP network is transmitted to the CT Bus and any DTMF digits are also sent. If the quality is not adequate, use out-of-band (OOB) DTMF transfer.
• H.245 UII messages from the application (gc_Extension( ) with an extension ID of IPEXTID_SENDMSG) are ignored.

When the PrmDTMFXferMode parameter is set to a value of 1, out-of-band (OOB) DTMF transfer is disabled and the following behavior applies:

• DTMF digits from the CT Bus are sent inband to the IP network.
• H.245 UII messages from the peer (containing out-of-band DTMF digits) are sent to the application.
• In-band DTMF digits are set to the CT Bus.
• H.245 UII messages from the application (gc_Extension( ) with an extension ID of IPEXTID_SENDMSG) are sent to the IP network.

The default value of the PrmDTMFXferMode parameter (2) is appropriate in most cases. However, in a terminate configuration, when it is necessary to send DTMF digits to the CT Bus and a voice channel (dxxxBwCz) is not available to play to the CT Bus, PrmDTMFXferMode can be set to 1.

Note: When out-of-band (OOB) DTMF transfer is disabled (PrmDTMFXferMode set to 1), the application can only send OOB DTMF digits (H245 UII messages) to the IP network. It cannot send DTMF digits to the CT Bus or inband DTMF digits to the IP network. Similarly, the application can only detect OOB DTMF digits, it cannot detect inband DTMF digits or DTMF digits from the CT Bus.

Two other possible values of the PrmDTMFXFerMode parameter are 0 and 3. A value of 0 disables DTMF transmission, while the value 3 is reserved for future use. See the "DTMF Parameters" section in the DM3 IPLink User's Guide for more information.

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