Sangoma phone only sends first DTMF tone

I have FreePBX running with a collection of Cisco SPA phones (508 and 525 models) and some Sangoma S500 phones. If we dial out on our phones to a number that requires keypress navigation of some sort (for sales press 1, please enter your account number, &etc.) the Cisco phones will work fine, but the Sangoma phones won’t. Further testing revealed the Sangoma phones will transmit the first key press tone, but no further tones are transmitted.

FreePBX version:
Trunk SIP settings (we use FlowRoute as our provider): dtmfmode=rfc2833
Sangoma Phone Firmware: 1.50 (
Using SIP, not PJSIP

In the config file for the Sangoma phones, here are all the entries relating to DTMF (we are only using account 1 on the phones)

    <P79 para="Account1.DtmfPayloadType">101</P79>
    <P20166 para="Account1.DtmfMode">0</P20166>
    <P1300 para="Preference.KeypadDTMFTone">0</P1300>
    <P20116 para="SuppressDTMF">1</P20116>
    <P20117 para="SuppressDTMFDelay">1</P20117>

Anyone have any suggestions on where to start troubleshooting this? Advice appreciated. Thanks in advance.

Since you have no issues with your Cisco phones, I suspect that this is an issue (or possibly a bug) with the Sangoma Phones.

I’d suggest you opening a ticket with Sangoma.

Keep us posted here as well…

Thanks, I’ll submit a ticket and respond with the results.

Also, my initial post stripped out the XML around the config options for the Sangoma phone; it should have read like this:
<P79 para=“Account1.DtmfPayloadType”>101</P79>
<P20166 para=“Account1.DtmfMode”>0</P20166>
<P1300 para=“Preference.KeypadDTMFTone”>0</P1300>
<P20116 para=“SuppressDTMF”>1</P20116>
<P20117 para=“SuppressDTMFDelay”>1</P20117>

I talked with Sangoma Support, and the problem was most likely that the latest firmware ( was not running on the S500. I had version 1.50 of the Sangoma firmware, which included, in Firmware Slot 1 for Sangoma phones in Endpoint Configuration. However, I had to change “Force Firmware Version” from Recommended to Firmware Slot 1 in the template of the phone before the firmware was finally sent to the phone and the phone updated. After was installed on the phone, the DTMF tones worked correctly.

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