Configuring DTMF Transport Types

The device supports various methods for transporting DTMF digits over the IP network to the remote endpoint for Gateway calls.

This feature is applicable only to the Gateway application.

The methods and their configuration can be configured on the DTMF & Dialing page (Setup menu > Signaling & Media tab > Gateway folder > DTMF & Supplementary > DTMF & Dialing):

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Using INFO message according to Nortel IETF draft: DTMF digits are sent to the remote side in INFO messages. To enable the mode:

Configure the 'Declare RFC 2833 in SDP' parameter to No (RxDTMFOption = 0).

Configure the 'First Tx DTMF Option' parameter to INFO Nortel (FirstTxDTMFOption = 1).

DTMF digits are removed from the audio stream (and the 'DTMF Transport Type' parameter is automatically set to Mute DTMF).

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Using INFO message according to Cisco’s mode: DTMF digits are sent to the remote side in INFO messages. To enable the mode:

Configure the 'Declare RFC 2833 in SDP' parameter to No (RxDTMFOption = 0).

Configure the 'First Tx DTMF Option' parameter to INFO Cisco (FirstTxDTMFOption = 3).

DTMF digits are removed from the audio stream (and the 'DTMF Transport Type' parameter is automatically set to Mute DTMF).

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Using NOTIFY messages according toIETF Internet-Draftdraft-mahy-sipping-signaled-digits-01: DTMF digits are sent to the remote side using NOTIFY messages. To enable the mode:

Configure the 'Declare RFC 2833 in SDP' parameter to No (RxDTMFOption = 0).

Configure the 'First Tx DTMF Option' parameter to NOTIFY (FirstTxDTMFOption = 2).

DTMF digits are removed from the audio stream (and the 'DTMF Transport Type' parameter is automatically set to Mute DTMF).

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Using RFC 2833 relay with Payload type negotiation: DTMF digits are sent to the remote side as part of the RTP stream according to RFC 2833. To enable the mode:

Configure the 'Declare RFC 2833 in SDP' parameter to Yes (RxDTMFOption = 3).

Configure the 'First Tx DTMF Option' parameter to RFC 2833 (FirstTxDTMFOption = 4).

To set the RFC 2833 payload type with a value other than its default, use the RFC2833PayloadType parameter. The device negotiates the RFC 2833 payload type using local and remote SDP and sends packets using the payload type from the received SDP. The device expects to receive RFC 2833 packets with the same payload type as configured by the parameter. If the remote side doesn’t include ‘telephony-event’ in its SDP, the device sends DTMF digits in transparent mode (as part of the voice stream).

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Sending DTMF digits (in RTP packets) as part of the audio stream (DTMF Relay is disabled): This method is typically used with G.711 coders. With other low-bit rate (LBR) coders, the quality of the DTMF digits is reduced. To enable the mode:

Configure the 'Declare RFC 2833 in SDP' parameter to No (RxDTMFOption = 0).

Configure the 'First Tx DTMF Option' parameter to Not Supported (FirstTxDTMFOption = 0).

Configure the ini file parameter [DTMFTransportType] to [2] (i.e., transparent).

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Using INFO message according to Korea mode: DTMF digits are sent to the remote side in INFO messages. To enable this mode:

Configure the 'Declare RFC 2833 in SDP' parameter to No (RxDTMFOption = 0).

Configure the 'First Tx DTMF Option' parameter to INFO Cisco (FirstTxDTMFOption = 3).

DTMF digits are removed from the audio stream (and the 'DTMF Transport Type' parameter is automatically set to Mute DTMF).

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The device is always ready to receive DTMF packets over IP in all possible transport modes: INFO messages, NOTIFY, and RFC 2833 (in proper payload type) or as part of the audio stream.

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To exclude RFC 2833 Telephony event parameter from the device's SDP, configure the 'Declare RFC 2833 in SDP' parameter to No.

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You can use the following parameters to configure DTMF digit handling:

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[FirstTxDTMFOption], [SecondTxDTMFOption], [RxDTMFOption], [RFC2833TxPayloadType], and [RFC2833RxPayloadType]

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[MGCPDTMFDetectionPoint], [DTMFVolume], [DTMFTransportType], [DTMFDigitLength], and [DTMFInterDigitInterval]