[VoIP] Seattle Museum?

[Donald Froula]

Yep, the phone generates it locally, for user feedback
only. Try listening from the terminating side.

Don

--- Steph Kerman <stfkerman at jps.net> wrote:

> That certainly makes sense but why then do I hear
> DTMF for the duration 
> of my keypress when doing end-end signaling? 
> Apparently the cellphone 
> itself is (also?) generating DTMF.
> 
> OTOH, people have used acoustically coupled DTMF
> tone generators with 
> considerable success for years.  Considering the
> high inherent 
> distortion level of the typical carbon transmitter
> and low distortion 
> component receiver tolerance specs required for
> rejecting digits to 
> prevent talk-off, that ought to work far less
> reliably than it does.
> 
> Steph
> 
> Donald Froula wrote:
> > On modern cell networks, the DTMF key press is
> converted to a message 
> > and sent over-the-air to the base station/network
> where the DTMF is 
> > regnerated at a fixed length, decided by your
> provider. Most of the 
> > codecs in use these days don't work too well for
> in-band tones. 
> > Although, I can whistle off my
> > ProjectMF server with 2600 HZ over a good cell
> connection!
> >
> > Don
> >
> > --- Steph Kerman <stfkerman at jps.net> wrote:
> >
> >> I've generally found that John Covert's portal
> works
> >> well, well enough 
> >> that I can even store the CNET number on a speed
> >> dial key and dial it 
> >> into CNET over his voice prompt or over the
> >> modulated dial tone.  I do 
> >> this after first dialing the PSTN access number
> for
> >> the portal itself 
> >> from another speed dial key. 
> >>
> >> I am also able to do this from my cellphone.  In
> the
> >> case of the 
> >> cellphone, the DTMF is passing over the cellular
> >> network first.  
> >> Amazingly, it works.
> >>
> >> Steph
> >   
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