Kevin P. Fleming wrote: > Steve Underwood wrote: > > >> Nice, but a nation by nation twist is slightly questionable. Applying >> twist at the source only seems to be appropriate for analogue paths. The >> way some countries specify it is kinda vague. A number of DTMF >> generators have a 2dB twist locked into them, but they were only ever >> intended for analogue connections. I would question whether a 2dB twist >> should ever be applied over a digital path. >> > > So what happens when that digital path becomes analog at the far end? > I'd be quite surprised if the far-end channel bank modified the audio to > achieve this. > The -2dB twist isn't intended to achieve a -2dB twist at the far end. Its to avoid it going highly positive, with the inevitable high frequency rolloff you get on analogue lines. Its just a compromise fudge, not something deeply engineered. If your local end isn't analogue, it makes no sense, regardless of what lies beyond. > In any case, I've only modified the zonedata for Brazil, because we've > gotten specific instructions from the regulatory agency there that there > must be 2dB twist whenever we generate DTMF. The rest of the zones are > still at -10/-10 (as they were before) and we'll only modify them when > we're really, really sure we should :-) Its very common practice all over the place. As I said before, some DTMF generators cannot even turn off that -2dB twist for any locale. You might find using that twist in any locale where you use analogue connections improves your DTMF reliability. The Brazilian spec is obviously based on a phone on an analogue line generating the DTMF. Have you been testing there with analogue or digital connections?
Regards, Steve _______________________________________________ --Bandwidth and Colocation Provided by http://www.api-digital.com-- asterisk-dev mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
