[asterisk-users] dtmf tones not always recognized

[Don Pobanz]

We have analog phones (Aastra 390) connected to channels banks (Adtran TA750) connected to a 4 port digium card( TE410P). 

Because of echo problems we purchased external T1 echo cancellers from Orion Telecom. (The TE412P did not eliminate enough of the echo). 

The Orioan echo cancellers eliminated our echo, however 5-15% of the time the first digit pressed is not recognized by * and the dialtone continues. By removing the echo cancellers, the dtmf works 100% of the time. 

By changing the losses and gains in the echo canceller, in the channel bank or in *, we can see changes in the % of recognized dtmf tones. (I believe, that if the 1st digit is recognized, then all of the following are recognized.)

Orion tells me that it is a volume issue since they have thousands of the same product in use elseware. (They have offered significant assistance in trouble shooting the probem). We also have a different location with no problems with the same setup. In fact we moved an echo canceller to that location and when set up the same it worked well. 

My thought is that the dialtone is interfering with the echo cancellers ability to pass the dtmf tones through cleanly. 

Is there a way to decrease the dial tone volume? 

Any other suggestions is appreciated!

Don Pobanz
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