thanks!
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Reply by Thomas Magma●June 30, 20052005-06-30
"xingyu" <anan_fox@21cn.com> wrote in message
news:Wv2dnbcphrmqnFnfRVn-pw@giganews.com...
> hi,all!
> i am working on a telephone program and i am new to DSP.i have search
> all the resource about "busy tone detect" and find i can use
> "Goertzel algoritm".but i don't know how to deal with the result of the
> "Goertzel",that is to say,i don't kown what is busy tone.so, can any one
> can give me the whole ideal for the process,or give you code about busy
> tone detect?
> thanks a lot!
>
>
>
> This message was sent using the Comp.DSP web interface on
> www.DSPRelated.com
The Goertzel is simply a very efficient band pass filter. You center it,
based on certain coefficients, on to your frequency of interest. It simply
kicks out a number that is representative of gain of that specific
frequency. For example, you would want to center it on 425Hz, and based on
your specific response time and detection certainties needs, you would write
software to determine the validity of that signal. For example, looking for
the characteristic 500ms on/off.
Thomas
Reply by Jim Thomas●June 30, 20052005-06-30
xingyu wrote:
> hi,all!
> i am working on a telephone program and i am new to DSP.i have search
> all the resource about "busy tone detect" and find i can use
> "Goertzel algoritm".but i don't know how to deal with the result of the
> "Goertzel",that is to say,i don't kown what is busy tone.so, can any one
> can give me the whole ideal for the process,or give you code about busy
> tone detect?
> thanks a lot!
Busy tone is different from one country to the next. In the US, it
consists of a 425 Hz tone chopped up with a cadence - that is, on for
0.5 seconds, off for 0.5 seconds. IIRC.
It is similar to the congestion tone (aka fast busy) which uses the same
frequencies, but a different cadence.
There is an ITU spec that documents the call progress tones (frequencies
and cadences) in most if not all countries, but I cannot remember which
one it is. Q.35?
These guys have some of the data online:
http://www.hellosoft.com/products/hellovoice/cpt.htm
Although the ITU would be a more authorative source and would include
international tones as well.
--
Jim Thomas Principal Applications Engineer Bittware, Inc
jthomas@bittware.com http://www.bittware.com (603) 226-0404 x536
Any sufficiently advanced technology is indistinguishable from magic.
- Arthur C. Clarke
Reply by xingyu●June 30, 20052005-06-30
hi,all!
i am working on a telephone program and i am new to DSP.i have search
all the resource about "busy tone detect" and find i can use
"Goertzel algoritm".but i don't know how to deal with the result of the
"Goertzel",that is to say,i don't kown what is busy tone.so, can any one
can give me the whole ideal for the process,or give you code about busy
tone detect?
thanks a lot!
This message was sent using the Comp.DSP web interface on
www.DSPRelated.com