[Asterisk-Users] Detecting DTMF tones

[matt.riddell at sineapps.com]

On 15 Sep 2004 at 1:52, San Singhania wrote:

> Hello everyone,
> 
> I am having big problems trying to detect dtmf tones while a IVR
> prompt is playing on zap channels. Sometimes the detection only starts
> 4-5 seconds into the prompts. Other times it works very well for the
> 1st few calls and then starts having problems. And most times it also
> does not detect all digits, eg when 123 is keyed in, it may detect 23
> or 2 or 3, but never the complete string. 
> 
> Can someone help me with this? I am in Singapore so I dont know if its
> a localisation issue. Also I have relexdtmf on and my rxgain and
> txgain on zap channels are set to 0 so i dont think thats the problem.
> 
> Help is most appreciated as I cannot go on with Asterisk if this
> function does not work :(
> 
Ok, I'm based here in New Zealand and found that the volumes for PSTN 
were quite a way off.

When I use spanDSP to send and receive faxes, I initially was able to 
get 10-20% through.  I used a New Zealand Telecom Fax testing number, 
where you send a fax and it sends you one back with and EQ chart for 
the line, volume received and sent in DB's and information about the 
line condition.

Using this information in conjunction with "/usr/src/zaptel/ztmonitor 
1 -v" meant that I could alter the txgain and rxgain until they were 
pretty optimal (within 1-2 db of what Telecom wanted).

I now receive 90%-95% of faxes absolutely fine. (as in correctly, not 
as in some new super fine resolution).

The reason I say this is that you may find that the txgain and rxgain 
need to be altered and if they are far enough off, may not detect 
DTMF reliably.

Don't forget you will need to do a "ztcfg -v" on the commandline and 
"restart now" in asterisk.  You can then just push the up arrow and 
press enter and the console will load.  I have a feeling that only 
ztcfg -v is actually required.

Cheers,

Matt Riddell
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