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Problems with DTMF - Knowledgebase / Troubleshooting - SIPcity Help Centre

Problems with DTMF

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Problems with DTMF

If you are reporting that your IVR is intermittently failing when pressing the menu selections of your Auto Attendant, it is highly likely that the in-house PBX has a DTMF issue.

In summary, you’ll need to ensure you are supporting RFC2833 and not the older analog Inband DTMF.

  • Inband: With Inband digits are passed along just like the rest of your voice as normal audio tones with no special coding or markers using the same codec as your voice. On a VoIP or SIP network, Inband is highly unreliable and is usually the cause of failure.

  • RFC2833: (Preferred setting in most cases) Is a standard definition for signaling for various events including DTMF tones, fax-related tones, and country-specific subscriber line tones.

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