Are you sure the sound he is hearing is not the modem fan screeching? :P
> -----Original Message-----
> From: Pete Resnick [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, June 11, 2002 1:37 PM
> To: Lloyd Wood
> Cc: Bill Cunningham; ietf
> Subject: Re: modems
>
>
> On 6/11/02 at 9:04 PM +0100, Lloyd Wood wrote:
>
> >You're confusing your modems and your acoustic couplers.
> >
> >An electrical transmission in the ~3.5kHz bandpass range that equates
> >to the dominant frequencies used by the human voice, which the phone
> >system was engineered to convert and carry easily, is not a sound.
> >Modulating an electrical signal into said electrical
> transmission does
> >not involve sound.
>
> OK, OK, of course that's exactly correct; almost all modems today
> completely bypass the issue of sound and transmit directly through
> the copper to the telephone switch. But let's get back to the
> question Bill was asking and why he was asking it:
>
> > On 6/11/02 at 3:22 AM -0400, Bill Cunningham wrote:
> >
> > >I know modems communicate on the physical layer by
> electrical pulses
> > >or binaries sent on copper wires.
>
> The important feature of modems is that they send analog signals over
> those lines, not digital (which is what I took Bill to mean by
> "binaries"). And those analog signals correspond quite directly to
> things that create sound (if connected to a speaker of the right
> sort) and receive sound (if taken from a microphone of the right
> sort). It is the correspondence to the receiving and production of
> sound that makes modems interesting devices; that's why acoustic
> couplers worked on the old modems. Similarly touch tones are *tones*
> because they can pass through a system designed for transmitting
> analog electrical signals that can be turned into a sound. (Hence,
> you could go out and by those touch-tone producing boxes, program
> phone numbers into them, hold them up to your phone receiver, and get
> the number dialed.)
>
> Yes, it is correct that most modems today deal with electrical
> transmission only and not sounds (except for their speakers). But it
> is the fact that those signals can easily become sounds that is key,
> at least to explain to Bill why his modem is screeching. (Although
> some of my friends in philosophy of science disagree, "explanation"
> is not a matter of reducing everything to physics.)
>
> It's times like this I think the IETF needs more academics. :-)
> --
> Pete Resnick <mailto:[EMAIL PROTECTED]>
> QUALCOMM Incorporated - Direct phone: (858)651-4478, Fax:
> (858)651-1102
>
>
