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

[Hans Witvliet]

On Sun, 2009-06-28 at 20:13 +0200, Andreas Sikkema wrote:
> On Jun 28, 2009, at 4:01 PM, Matt Florell wrote:
> > 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.
> 
> I'm very careful with my ancient telephone which has a full DTMF  
> keyboard exactly for this purpose. It's also a lot of fun to test on  
> ATAs.
> 
> Unfortunately it's only allowed to be used on  
> Fernsprechernebenstellenanlagen, so I can use it anywhere I like, I  
> have no idea what those are ;-)
> 
(lost the original message)
I have been working for a company that menufactured telco equipment.
We used the a,b,c,d-DTMFsignals to activated certain parts of the
dialplan in PABX's.
So phones intented to be used behind a pabx would heve those keys, while
phoned connected directly to the public net would have dummy buttons or
no buttons at all at those positions.
Nowadays these keys are often not used anymore.

Thats the reason why you don't find that many phones with thoses
buttons: There were never that much produced, compared with the "normal"
ones without them. 
Some softphones also have those extra four keys...

Hans