[asterisk-dev] Can Asterisk detect A,B,C,D DTMF signals

[Kaloyan Kovachev]

Hi,

On Sun, 28 Jun 2009 10:01:25 -0400, Matt Florell wrote
> Hello,
> 
> One of our clients uses "A" quite a bit internally, the Zoiper
> softphone has it right in the key-pad, and they use it for internal
> extensions like voicemail and timeclock applications through Asterisk.
> As for the others, I have heard of success with B and C, but some
> issues with the D key in Asterisk.

Not sure here about Asterisk, but some systems use D as a flash key to perform
a transfer

> 
> As a side note, these DTMF signals have been around for decades, most
> telco infrastructure equipment supports these signals, and you can
> find very old linesman's handsets that have the A-D row of buttons on
> them.
> 
> http://en.wikipedia.org/wiki/Dtmf#.23.2C_.2A.2C_A.2C_B.2C_C.2C_and_D
> 
> MATT---
> 
> On 6/28/09, Nir Simionovich <nir.simionovich at gmail.com> wrote:
> > Hi All,
> >
> > I've been asked by a prospect if Asterisk can handle the additional DTMF
> > signals that
> > may be produced by some emergency systems. According to the DTMF standard,
> > there are 4 additional tones that can be generated, however, these are not
> > used in most
> >  phones.
> >
> > Can these be intercepted by Asterisk?

Yes, look at dsp.c around line 270:

static float dtmf_row[] =
{
	697.0,  770.0,  852.0,  941.0
};
static float dtmf_col[] =
{
	1209.0, 1336.0, 1477.0, 1633.0
};

... so you have all the 4 rows and columns recognized with 1633.0 being the
one for A,B,C,D

> >
> > Nir Simionovich
> >
> >
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