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From: RalfM on 10 Mar 2010 20:44
Hi, here's some beginners questions:

digital data transfer on a wired copper medium is done usually by setting
a DC voltage (for example 5V) for a defined duration to indicate
a binary 1 value, and say 0V to indicate binary 0.
I think the duration of such a signal is called "bit period".

Here are some questions & thoughts:
What are the chips doing this switching for transmitting are called? (modulator? DAC?)
How is it done one the receiving side? (via an ADC ?)
How many such binary signals can a say 2 GHz CPU generate in real-world per second?

Such a bitwise transfer does need only a fast switching between 2 voltage levels.
Is it possible to have a transmitter/receiver that can use more than
just 2 possible values per "bit period" (for example: a 12-bit ADC or DAC
can detect 2^12=4096 different values (ie. voltages). Then why use
only 2 values (0/1) in copper wired data transfers instead of using
say 256 or 512 or 1024 or 2048 or 4096 bits etc.? (ie. make the cable a "8 bit cable" :-) or more.
IMHO one could dramatically increase the speed on wired copper medium
(for example a 256-fold increase or even more would be possible).
Are there such chips which can switch fast a voltage source say to 256
different values? ie. fast DAC and ADCs, DSP maybe?

Just some crazy thoughts of mine... :-)

From: Jim Stewart on 11 Mar 2010 13:12
RalfM wrote:
> Hi, here's some beginners questions:
>
> digital data transfer on a wired copper medium is done usually by setting
> a DC voltage (for example 5V) for a defined duration to indicate
> a binary 1 value, and say 0V to indicate binary 0.
> I think the duration of such a signal is called "bit period".
>
> Here are some questions & thoughts:
> What are the chips doing this switching for transmitting are called?
> (modulator? DAC?)
> How is it done one the receiving side? (via an ADC ?)
> How many such binary signals can a say 2 GHz CPU generate in real-world
> per second?
>
> Such a bitwise transfer does need only a fast switching between 2
> voltage levels.
> Is it possible to have a transmitter/receiver that can use more than
> just 2 possible values per "bit period" (for example: a 12-bit ADC or DAC
> can detect 2^12=4096 different values (ie. voltages). Then why use
> only 2 values (0/1) in copper wired data transfers instead of using
> say 256 or 512 or 1024 or 2048 or 4096 bits etc.? (ie. make the cable a
> "8 bit cable" :-) or more.
> IMHO one could dramatically increase the speed on wired copper medium
> (for example a 256-fold increase or even more would be possible).
> Are there such chips which can switch fast a voltage source say to 256
> different values? ie. fast DAC and ADCs, DSP maybe?
>
> Just some crazy thoughts of mine... :-)

Wouldn't that be the same as the difference
between telephone and telegraph?
From: RalfM on 11 Mar 2010 13:44
Grant Edwards wrote:
> On 2010-03-11, RalfM<rm(a)invalid.invalid> wrote:
>
>> digital data transfer on a wired copper medium is done usually by
>> setting a DC voltage (for example 5V) for a defined duration to
>> indicate a binary 1 value, and say 0V to indicate binary 0. I think
>> the duration of such a signal is called "bit period".
....
>> (for example: a 12-bit ADC or DAC can detect 2^12=4096 different
>> values (ie. voltages). Then why use only 2 values (0/1) in copper
>> wired data transfers instead of using say 256 or 512 or 1024 or 2048
>> or 4096 bits etc.?
>
> That called a modem. They use a sometimes large set of
> phase/amplitude to encode multple bits per symbol. Using
> phase/amplitude instead of DC level allows the signal to be
> transmitted over media that won't carry DC.

Doesn't Ethernet use DC?
And Ethernet uses bit-serial transfer at the lowest physical level.
What I mean is to replace the bit-serial part by say a byte-serial transfer.
Ie. in the same transfer cycle (time) now 8 bits could be transferred (insted of just 1)
by using more than 2 DC signalling levels (here 8), much like how a DAC
and ADC do it.
From: RalfM on 11 Mar 2010 13:51
WangoTango wrote:
> In article<hn9i18$m3h$1(a)speranza.aioe.org>, rm(a)invalid.invalid says...
>>
>> Just some crazy thoughts of mine... :-)
>
> http://en.wikipedia.org/wiki/Constellation_diagram

Isn't this intended for AC signals? I was meaning DC signals like in Ethernet.
From: RalfM on 11 Mar 2010 13:57
Don Bruder wrote:
> In article<hn9i18$m3h$1(a)speranza.aioe.org>, RalfM<rm(a)invalid.invalid>
> wrote:
>
>> Such a bitwise transfer does need only a fast switching between 2 voltage
>> levels.
>> Is it possible to have a transmitter/receiver that can use more than
>> just 2 possible values per "bit period" (for example: a 12-bit ADC or DAC
>> can detect 2^12=4096 different values (ie. voltages). Then why use
>> only 2 values (0/1) in copper wired data transfers instead of using
>> say 256 or 512 or 1024 or 2048 or 4096 bits etc.? (ie. make the cable a "8
>> bit cable" :-) or more.
>> IMHO one could dramatically increase the speed on wired copper medium
>> (for example a 256-fold increase or even more would be possible).
>> Are there such chips which can switch fast a voltage source say to 256
>> different values? ie. fast DAC and ADCs, DSP maybe?
>>
>> Just some crazy thoughts of mine... :-)
>
> Congratulations - You've just re-invented analog transmission.

Hmm. isn't analog transmission using AC? I mean use DC like in Ethernet
but instead of transmitting just 1 bit per cycle use instead say 8 bits per cycle,
ie. 8 DC voltage levels much like done with a DAC and ADC.
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