Need way to filter out double DTMF signals

question

New Member
Mar 30, 2026
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New install with updates on Debian 13. It was working OK with one number. Direct Dial is disabled, instead I put the extension number as an option. The Destination Action sends it to the IVR. The user enters the extension number.

I want to replace the number with a different number. I changed the number in Extensions and Destinations. When I dial the extension the error message plays and it hangs up. I put the original number back and it worked OK again.

So I added a new Destination and new Extension for the new number and it worked. I deleted the old number extension and destination and the new number extension still worked.

I rebooted and it is back to playing the error message and hangs up.

If I route the incoming call to directly to the extension instead of the IVR it will work.

The IVR is messing up the dialed extension, in this case I dialed '1' '0' '3'. When I press '1' it thinks it received "1' '1'. Then on '0' it receives double digits again and calls it an invalid input. Extension digits is set to 3. Here is output of fs_cli.

Code:
2026-06-14 18:39:05.855188 96.67% [DEBUG] switch_ivr_play_say.c:2013 done playing file /var/lib/freeswitch/recordings/4dy.link/please-enter-the-extension-8k.wav
2026-06-14 18:39:05.855188 96.67% [DEBUG] switch_ivr_menu.c:378 waiting for 3/3 digits t/o 2000
2026-06-14 18:39:05.855188 96.67% [DEBUG] switch_ivr.c:1385 Codec Activated L16@8000hz 1 channels 20ms
2026-06-14 18:39:06.795171 96.67% [DEBUG] switch_rtp.c:7961 RTP RECV DTMF 1:1120
2026-06-14 18:39:06.795171 96.67% [INFO] switch_channel.c:529 RECV DTMF 1:1120
2026-06-14 18:39:07.095177 96.67% [DEBUG] switch_rtp.c:7961 RTP RECV DTMF 1:800
2026-06-14 18:39:07.095177 96.67% [INFO] switch_channel.c:529 RECV DTMF 1:800
2026-06-14 18:39:07.555198 96.33% [DEBUG] switch_rtp.c:7961 RTP RECV DTMF 0:1120
2026-06-14 18:39:07.555198 96.33% [INFO] switch_channel.c:529 RECV DTMF 0:1120
2026-06-14 18:39:07.555198 96.33% [DEBUG] switch_ivr_menu.c:425 digits '110'
2026-06-14 18:39:07.555198 96.33% [DEBUG] switch_ivr_menu.c:659 IVR menu '8388c92b-63d9-4b54-bd0d-ff7fc2d9de42' caught invalid input '110'
2026-06-14 18:39:07.555198 96.33% [DEBUG] switch_ivr_play_say.c:1564 Codec Activated L16@8000hz 1 channels 20ms
2026-06-14 18:39:07.635176 96.33% [DEBUG] switch_rtp.c:690 TS changed from last packet, resetting....
2026-06-14 18:39:07.695188 96.33% [DEBUG] switch_rtp.c:7961 RTP RECV DTMF 0:960
2026-06-14 18:39:07.695188 96.33% [INFO] switch_channel.c:529 RECV DTMF 0:960
2026-06-14 18:39:07.695188 96.33% [DEBUG] switch_ivr_play_say.c:2013 done playing file /usr/share/freeswitch/sounds/en/us/callie/misc/error.wav
2026-06-14 18:39:07.695188 96.33% [DEBUG] switch_ivr_play_say.c:1564 Codec Activated L16@8000hz 1 channels 20ms
2026-06-14 18:39:08.075178 96.33% [DEBUG] switch_rtp.c:7961 RTP RECV DTMF 3:1120
2026-06-14 18:39:08.075178 96.33% [INFO] switch_channel.c:529 RECV DTMF 3:1120
2026-06-14 18:39:08.075178 96.33% [DEBUG] switch_ivr_play_say.c:2013 done playing file /var/lib/freeswitch/recordings/4dy.link/please-enter-the-extension-8k.wav
2026-06-14 18:39:08.075178 96.33% [DEBUG] switch_ivr_menu.c:378 waiting for 2/3 digits t/o 2000
2026-06-14 18:39:08.075178 96.33% [DEBUG] switch_ivr.c:1385 Codec Activated L16@8000hz 1 channels 20ms
2026-06-14 18:39:08.255168 96.33% [DEBUG] switch_rtp.c:7961 RTP RECV DTMF 3:1120
2026-06-14 18:39:08.255168 96.33% [INFO] switch_channel.c:529 RECV DTMF 3:1120
2026-06-14 18:39:10.255175 96.27% [DEBUG] switch_ivr_menu.c:425 digits '33'
2026-06-14 18:39:10.255175 96.27% [DEBUG] switch_ivr_menu.c:659 IVR menu '8388c92b-63d9-4b54-bd0d-ff7fc2d9de42' caught invalid input '33'
2026-06-14 18:39:10.255175 96.27% [DEBUG] switch_ivr_play_say.c:1564 Codec Activated L16@8000hz 1 channels 20ms
2026-06-14 18:39:12.255213 96.27% [NOTICE] sofia.c:1065 Hangup sofia/internal/+15412866144@4dy.pstn.twilio.com:5060 [CS_EXECUTE] [NORMAL_CLEARING]
2026-06-14 18:39:12.255213 96.27% [DEBUG] switch_ivr_play_say.c:2013 done playing file /usr/share/freeswitch/sounds/en/us/callie/misc/error.wav
 
Last edited:
This is looking like a problem of the SIP provider sending two DTMF signals per key-press for the problem number. It would be fixable on the PBX side if there was a debounce setting which would ignore a button presses too close together. For example ignore a DTMF that is less than 50 ms after the last one.