No it is not, the nominal tone length is 40mS, with some telecomunication
Auhs asking for 20mS. Note that the longer the line and the more the noise
the shorter the detection period required. Talk to Alcatel and AT&T about
this, also see Austell TS003/3/7 and 26? (Not sure about that one)

Dennis



> -----Original Message-----
> From: David VanHorn [SMTP:dvanhorn@CEDAR.NET]
> Sent: Thursday, 25 May 2000 3:23
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: DTMF Decoding with a PIC (sigma-delta)
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
>
> >        Yes the amount of processing power to decide the DTMF tone is
> >"smallish", however, the external ADC is excessive, and on top of that we
> >have only a 20mS period in which to decide what DTMF tone it is! (Worst
> >case), with levels down to -26dBmO
>
> ???  DTMF dialing is speced at 10 dps, which is usually implemented as
> 50mS
> on, 50mS off.  I've not seen any decoders that work reliably with less
> than
> 40mS
>
>
>
> - --
> Are you an ISP?  Tired of spam?
> www.spamwhack.com  A pre-emptive strike against spam!
>
> Where's Dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9
>
> -----BEGIN PGP SIGNATURE-----
> Version: PGPfreeware 6.5.2 for non-commercial use <http://www.pgp.com>
>
> iQA/AwUBOSwP3IFlGDz1l6VWEQIk8ACgomeiZlYVRHVQPyBnuwLjuC4zOOAAn05q
> zzWVxCSkmJ+s9RfTw7ZRV8IW
> =lT5U
> -----END PGP SIGNATURE-----