6.4 Generating DTMF

Once DTMF mode has been configured, the application can generate DTMF digits using the ipm_SendDigits( ) function.

Note: The only supported direction for DTMF digit generation is towards the TDM bus.

Alternatively, the ipm_SendRFC2833SignalIDToIP( ) function can be used to send RFC 2833 data to the IP network.

Note: The ipm_SendRFC2833SignalIDToIP( ) function is not supported on Intel® NetStructure™ IPT Series boards. In this case, once you set the mode to RFC 2833, the only way to send an RFC 2833 digit is to have the ipmBxCy device listening to a TDM time slot. If the ipmBxCy device detects a digit from the TDM time slot, it will convert it to RFC 2833 and transmit the digit over RTP.

A typical use of the ipm_SendRFC2833SignalIDToIP( ) function is to:

• fill in the IPM_RFC2833_SIGNALID_INFO structure with the signal (tone) to send and the signal state set to SIGNAL_STATE_ON to start generating DTMF.
• call ipm_SendRFC2833SignalIDToIP( ) to indicate the start of the data
• wait an appropriate amount of time (for example, 50 msec)
• fill in the IPM_RFC2833_SIGNALID_INFO structure with the signal (tone) to stop and the signal state set to SIGNAL_STATE_OFF to stop generating DTMF.
• call ipm_SendRFC2833SignalIDToIP( ) to indicate the end of the data

This scenario is useful in situations when the application receives ringback from the PSTN and needs to send the tone data to the IP network. The application uses voice library functions to detect ringback. (See the Voice API Library Reference for more details.) Then the application sets the RFC2833 signal on and leave it on until the ringback stops.

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