pretty much OT: acoustic coupling

Randy Dawson rdawson16 at
Sat Mar 24 20:50:16 CDT 2007

Hey Fred,

I think you should review Claude Shannon, if we are going to get into a bits 
per bandwidth argument.

I think the bell 103, 203 standards for modems were still 1200, 2400 FSK 
even if the baud was 110.

Thanks Fred, for reply, this modem stuff is my favorite topic at the moment. 
  I am working on my own implementation of all of these in a DSP.


>From: Fred Cisin <cisin at>
>Reply-To: "General Discussion: On-Topic Posts Only" <cctech at>
>To: "General Discussion: On-Topic and Off-Topic Posts" 
><cctalk at>
>Subject: Re: pretty much OT: acoustic coupling
>Date: Sat, 24 Mar 2007 18:18:50 -0700 (PDT)
> >  What is the typical maximum
> > speed of such a device,
>'twould seem that anything that goes through an analog/voice phone line
>should work with acoustic coupling
>OTOH, if you want to do FSK (Frequency shift keying), and want to do it by
>counting cycles to differentiate the different tones, then think about how
>many cycles you would need to identify a tone.  If it is equal to, or more
>than 1, then you're not going to get more bits per second than the lowest
>tone's number of cycles per second.  Therefore, you need to play games
>with more than one bit per audio tone to get past about 1200 bits per

It’s tax season, make sure to follow these few simple tips

More information about the cctech mailing list