Troubleshooting DTMF

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Phone Number to Call and Test DTMF

Need a number to test DTMF, try calling 631-791-8378. It will read back each DTMF digit that you dial. Follow the instructions to get to DTMF testing.

Ensure DTMF Mode is set properly on Phones

  • For HD Phones ensure their DTMF Mode is set to RFC2833. This is set under Extension->Advanced.
  • For IP550 and IP120 Phones set their DTMF Mode to SIP INFO.
  • Ensure that the phones are configured through the PBX. If they are manually configured then you need to set the DTMF setting in the PBX and in the phone.

Internal Voicemail / IVR(Menu)

We have found that in some environments, ambient noise can cause automatic DTMF mode detection to mistake the mode for inband.  The best solution to this is to navigate to PBXSetup->SIP and under Advanced set DTMF mode to RFC2833.

External IVR

If the issue you are troubleshooting involves dialing * or # into an external IVR, you can navigate to PBXSetup->General and change the value for Feature Digit Timeout.

This value is in milliseconds. It determines how long after you press a feature code digit, the PBX will wait before it sends the code as normal DTMF. Because ## and *# are feature codes, the PBX does not immediately send them. It waits temporarily to see if you are going to dial the complete feature code.

If you set it below 200, humans cannot manually activate features codes in most cases, but most phones can. Note the ## transfer feature code is used for call park keys on phones. If you change the feature digit timeout, save, apply. Then try to park a call by calling from Phone A to Phone B and pressing the Park key on Phone B.

Global DTMF Setting

In some instances if may provide better performance when accessing voicemail, to set the default DTMF mode to RFC2833.  To do thisL

  1. Navigate to PBXSetup->SIP and click Advanced
  2. Locate DTMF Mode and set it to RFC2833.
  3. Save at the bottom of the page, then press Apply Changes

Note you will have to restart any calls for the changes to take effect.

Mass Edit DTMF

Mass_Edit_DTMF_Mode Quick Guide