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Joined: Feb 2023
Posts: 1
OP Offline
Joined: Feb 2023
Posts: 1

We have been doing this for 12+ years...
Something odd is happening.

We use Grandstream HT814 and HT818 most of the time.
Usually with an NEC SL1100 or SL2100 to provide the dial tone.

I have 2 customers...with the same set up.
1. SL2100
2. Grandstream ATA
3. Verizon FiOS

DTMF has gone wonky.
When a caller hits the auto attendant, the system doesn't recognize DTMF.
Calls time out to the operator phone.

This doesn't happen anywhere else.
And we have plenty of systems out there.

Any ideas for this?
I've tried forums, SL tech support...nothing solves it.


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Joined: Jun 2005
Posts: 2,706
Likes: 7
Joined: Jun 2005
Posts: 2,706
Likes: 7

I've had problems with DTMF on Auto Attendants with other systems, especially with VoIP.

So the ATAs are converting VoIP to analog into the NEC PBX?

I think the first thing to figure out is if the DTMF is coming in as RTP audio, RFC2833 or SIP Info. If the DTMF is coming in as part of the RTP audio stream, maybe it's getting mangled through compression (G729) where the NEC can't decifer the tone. If it's RFC2833, then the ATA should be converting the DTMF digits back into DTMF tones for the PBX.

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