TELECOM Digest OnLine - Sorted: Re: Packet8 DTMF Tones Sound "Clipped"

Re: Packet8 DTMF Tones Sound "Clipped"

Clark W. Griswold, Jr. (
Mon, 23 May 2005 17:58:50 -0600 wrote:

> I hooked up a line analyzer and listened to the call, and all
> I'm hearing on my end is a "blip blip blip" as he repeatedly presses
> the key to save the message. The DTMF tone basically sounds like it
> was clipped at just a few milliseconds

I seem to recall that the old Bell System spec for tone duration was
20ms, or 1/5th of a second. Some switches allowed you to go as fast as
10ms, which put the speed in speedial. :)

Don't know how P8 generates tones, but is it possible they are right
at the lower spec limit and your system isn't capable of decoding at
that rate?

OTOH, since P8 needs to generate the tones, its possible they aren't
under certain circumstances. Again, back some years DTMF tones (MF
actually) were suppressed in some circumstances as a fraud control
measure when inband signalling was used. No one should be doing that
now, but ...

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