my understanding is that standard phone calls run at about 64kbps data rate.

in Australia at least the carriers only guarantee the call to 9600bps
the improvement in modem speeds has been finding better ways to utilise the
line, better modulations etc. The compression and error checking runs on top
of that. I've had uploads of 30k/s on a 56k modem (which only connect at
33.6k up stream btw) due to the compression the modem was doing.

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Ian McLean
> Sent: Wednesday, 21 January 2004 11:06 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE] Why don't baud rates just double?
>
>
> There is quite a lengthy history behind this.  To summarise in a crude
> fashion, telephone lines can only really handle about 9600 max.  By using
> some clever compression and error handling techniques, they increased the
> speed to 14.4k, 28.8k and then 33.6k.  Then, hitting a barrier with that
> technology, by rethinking the problem and using DSP to handle some really
> clever compression, they upped the speed again to 56k, which started with
> 56k flex, and then the very clever V.90.  Then, by rethinking the problem
> completely again, introduced FFT and cleverer DSP's, and came up
> with ADSL.
> I think this explains why thinks get different after 9600 baud.  The guys
> who invented these techniques were indeed very clever.
>
> Rgs
> Ian.
>
> > -----Original Message-----
> > From: pic microcontroller discussion list
> > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of James Newton, Host
> > Sent: Wednesday, 21 January 2004 11:18 am
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: [EE] Why don't baud rates just double?
> >
> >
> > Why is each higher baud rate twice as fast until 14.4K which
> > is only 1.5
> > times faster than 9600?
> >
> > 115,200
> >  57,600
> >  28,800
> >  14,400
> >     ?
> >   9,600
> >   4,800
> >   2,400
> >   1,200
> >     600
> >     300
> >
> > ---
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