[Coco] Coco Modem phone line connection

[Alex Evans]

Phones don't use time division multiplexing, and neither do classic
analog modems. If we look at the simple case of a 300 baud modem, it
manages full duplex because it uses four different tones, two for the
answer side and two for the originate side with one tone one each side
for 0 and a different one for each side for a 1. Originate uses 1070
and 1270 Hz while answer uses 2025 and 2225 Hz. You could call it
frequency division multiplexing.

On Sun, Dec 1, 2019 at 9:42 AM Dave Philipsen <dave at davebiz.com> wrote:
>
> Actually you can talk full duplex on two telephones by simply connecting
> them both to the same relatively high impedance power supply. I think
> time division multiplexing is what allows multiple signals
> (conversations) to share the same path or pair of wires.
>
> Dave
>
>
> On 11/30/2019 8:43 PM, Joel Rees wrote:
> > Time multiplexing, as I understand it.
> >
> >
> > 2019年11月20日(水) 13:39 Dave Philipsen <dave at davebiz.com>:
> >
> >> Yes, in much the same way in which one line allows you to both speak and
> >> listen at the same time (full duplex) using a standard voice telephone.
> >>
> >> Dave
> >>
> >>> On Nov 19, 2019, at 10:43 AM, rietveld rietveld <rietveldh at hotmail.com>
> >> wrote:
> >>> Does one line do both receive and send of the data?
> >>>
> >>> Sent from my BlackBerry
> >>>   Original Message
> >>> From: Gene Heskett
> >>> Sent: Tuesday, November 19, 2019 11:25 AM
> >>> To: coco at maltedmedia.com
> >>> Reply To: CoCoList for Color Computer Enthusiasts
> >>> Subject: Re: [Coco] Coco Modem phone line connection
> >>>
> >>>
> >>>> On Tuesday 19 November 2019 11:17:10 rietveld rietveld wrote:
> >>>>
> >>>> It looks like the coco only uses the middle two wires(red and green)
> >>>> on a four line phone cord.   Is this correct?
> >>>>
> >>> Probably, since thats all it takes to run a telephone.
> >>>
> >>>> Sent from my BlackBerry
> >>>
> >>> Cheers, Gene Heskett
> >>> --
> >>> "There are four boxes to be used in defense of liberty:
> >>> soap, ballot, jury, and ammo. Please use in that order."
> >>> -Ed Howdershelt (Author)
> >>> If we desire respect for the law, we must first make the law respectable.
> >>> - Louis D. Brandeis
> >>> Genes Web page <http://geneslinuxbox.net:6309/gene>
> >>>
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> >>
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>
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