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No DTMF on FritzBox

Sunshine

Member
Hi, hoping there's some fellow FritzBox users here.

I have a FritzBox 7530 connected to my own SIP server, with a BT digital voice handset connected to it.

So, when you type in the number you want to call on a regular landline plugged into a socket/ata/router, you can usually here the dial tone then the phone playing the DTMF tones down the line

However, when a dect phone is connected to the FritzBoxs, it just makes the dial tone but no DTMF sounds but still rings the number. Hopefully that makes sense

Has anyone else experienced this? Is it a known issue? Can it be changed?
 
However, when a dect phone is connected to the FritzBoxs, it just makes the dial tone but no DTMF sounds but still rings the number.
That is expected behaviour:

on a DECT phone, you enter the number you want to call. Once the number is complete, you press the green button. You won't hear DTMF tones as there are none involved in the signalling between the DECT handset and DECT base. When you press the green button the DECT phone sends the entire number string to the DECT base.

It may be possible that on some DECT phones (connected to a POTS line) that you press the green button first, hear a dial tone from the exchange and then dial the number. In this case you might hear DTMF tones for each digit sent to the exchange one by one.

You should, however, hear DTMF tones during a call, e.g. when you enter your account number in telephone banking.
 
That is expected behaviour:

on a DECT phone, you enter the number you want to call. Once the number is complete, you press the green button. You won't hear DTMF tones as there are none involved in the signalling between the DECT handset and DECT base. When you press the green button the DECT phone sends the entire number string to the DECT base.

It may be possible that on some DECT phones (connected to a POTS line) that you press the green button first, hear a dial tone from the exchange and then dial the number. In this case you might hear DTMF tones for each digit sent to the exchange one by one.

You should, however, hear DTMF tones during a call, e.g. when you enter your account number in telephone banking.
When the BT digital voice phones are connected to the BT hub, they act like a normal landline phone - it plays the dial tone then you hear the DTMF tones as it dials

Is it unique to the FritzBox?
 
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I suspect the BT Digital Voice platform is configured to play the tones back at you since that is what people are used to hearing on their analogue landlines and they'd get support cases about how the buttons aren't working if people couldn't hear the sounds. There might be options within the Fritzbox to use in-band DTMF, and this might make the noises play down the phone in a way that you can hear them.
 
If I connect a wired phone to the Fritzbox, I can hear the DTMF tones in the handset when dialling a number. The DTMF tones are generated by the phone and then just echoed by the Fritzbox (just as if you had a POTS landline) even if the call goes out on VoIP.

I suspect the BT Digital Voice platform is configured to play the tones back
It would not surprise me if BT did something differently :)
There might be options within the Fritzbox to use in-band DTMF, and this might make the noises play down the phone in a way that you can hear them.
That option does not exist, it simply won't work with DECT as you enter the complete number and then press the green button. Only at that point is the signalling message sent from the DECT phone to the Fritzbox.
 
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