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Q: WHAT is actually sent from 1 computer to another? ( Answered,   10 Comments )
Subject: WHAT is actually sent from 1 computer to another?
Category: Science > Technology
Asked by: wumply-ga
List Price: $2.00
Posted: 29 Mar 2006 19:25 PST
Expires: 28 Apr 2006 20:25 PDT
Question ID: 713418
Can I be directed to sites that hopefully will precisely answer my
question?  Here it is: As I currently understand things...

A "1" represents a voltage; it pushes electrons over computer wires
and eventually over a communications network.  A "0" represents a "no
voltage"... nothing is happening--no electronics moving along the

So is the transmission of information from my computer to say a host
computer a changing series of electron flow periods interspersed with
a periods of "no electron" flow periods depending on the sequence of
voltages and 'no voltages' presented?

And at the receiving computer's end, the circuitry there distinguishes
between a voltage and a 'no voltage' and says: "Oh, I've got a "1" and
a "0"?

So, assuming the above is correct, I can conclude/summarize that what
actually goes on in transmission of information is that electrons move
along the communications network but that also there are periods when
electrons do not move over the wires and the transistors and chips or
circuits (whatever) can distinguish between electron flow and "no
electron" flow?  And thus our ones and zeros get from A to B?   And in
fiber optic lines you simply have a light impulse vs "no impulse"
replacing a electron flow vs "no electron flow"?

Or HOW DOES it work? 

And if any readers of this question are tempted to comment I hope they will!
Subject: Re: WHAT is actually sent from 1 computer to another?
Answered By: hedgie-ga on 17 Apr 2006 23:58 PDT
Your grasp is correct, and comments are good, but you did not
expire the question, so I will try to find what you asked for,
namely few links which explain the process.

But first, comment about electrons: those are always moving,
quite fast, depending on temperature (of the wire). When voltage is
applied (to the two ends of the wire) the 'drift velocity' is added to the
thermal motion.

That's Ohm's law.

Now few links on networks:
There are 7 layers

You are interested in the lowest, physical layer

which can be implemented by wire, fiber optics, emg (wireless radio) link etc

Here is 'a practical guide' how to do 'the cabling'

and here (good visual) presentation of those marching bits

You will get more references when you enter into search engine
 SEARCH TERMS: OSI, Physical Layer

combined with : fiber, electric, voltage, etc

Rating appreciated.

Subject: Re: WHAT is actually sent from 1 computer to another?
From: probonopublico-ga on 29 Mar 2006 20:55 PST
Of course, you don't need 'wires' ... There's no wire connecting my
computer with yours ... At least, none that I can see even though
there's a MASS of wires behind my desk.

I'm beginning to wonder ... What are all those wires for?
Subject: Re: WHAT is actually sent from 1 computer to another?
From: kottekoe-ga on 29 Mar 2006 21:57 PST

Yes, you grasp the concept correctly. In reality things are a little
more complicated and variable, but the scheme you describe is one way
that works. The "1" and "0" (which we could just as well, and often
do, call "true" and "false", or "high" and "low") can be represented
in many ways. In some systems a "1" is a positive voltage, while a "0"
is a negative voltage. In other systems the "1" might be a voltage
that oscillates at a particular frequency, or a voltage that goes up
during a particular interval of time. As you point out, a "1" can also
be a flash of light. On a disk drive, a "1" could be a tiny magnet
with its north pole pointed "up". On a DRAM a "1" is a bunch of
electrons on a tiny capacitor plate. In a radio link or DSL
connection, you often use many different codes instead of just two.
For example, each transmitted symbol might be one out of 256 symbols
uniquely represented by the amplitude and phase angle of a rapidly
oscillating signal. The beauty of it all is that information of any
kind can be represented arbitrarily well with a finite number of these
"bits" (binary digits) of information.
Subject: Re: WHAT is actually sent from 1 computer to another?
From: sorwin-ga on 30 Mar 2006 14:44 PST
It is NOT helpful to regard logical "1" or "0" as represented by
voltage levels.  Such representation may or may not be correct,
depending upon circumstances.

"1" and "0" usually represent binary numbers in Boolean algebra, for example:
000  =  0
001  =  1
010  =  2
011  =  3
100  =  4
101  =  5
110  =  6
111  =  7
and so-on.

The above shows binary numbers in 3-bit bytes.  Most PC's use 32-bit
bytes, so the maximum number conveyed by a 32-bit byte is 2 to the
power 32 minus 1
  =  4294967295

What the numbers represent could be anything and depends upon the
application and its context.
Subject: Re: WHAT is actually sent from 1 computer to another?
From: kottekoe-ga on 30 Mar 2006 18:21 PST

On the contrary, if you are trying to understand how a computer works,
like Wumbly, it is quite useful to think of "1" and "0" as
representing voltage levels. In many cases that is how the bits are
encoded. On a CMOS chip, where most of the computing happens, that is
exactly how it works. The MOS transistor is controlled by a voltage
and used to produce a voltage to drive the next level of logic.

P.S. A byte is always 8 bits, by definition. A "word" can be any length.
Subject: Re: WHAT is actually sent from 1 computer to another?
From: wumply-ga on 01 Apr 2006 18:14 PST
So kottekoe-ga, would you confirm or correct THIS...since I want to be
very sure.  Instead of using a positive voltage for a "1" and a "no
voltage" for a "0" we used a +2 voltage for a "1" and a -2 for a "0",
it's truly's the same electron flow/no electron flow?

Yes, it is pretty darned amazing!
Subject: Re: WHAT is actually sent from 1 computer to another?
From: kottekoe-ga on 01 Apr 2006 22:32 PST

Yes, you could use +2 V and -2 V as your logic levels if there was a
good reason to do so. Since no voltage are ever exact, you might
define +2 V and -2 V as the nominal values, but allow anything above
+1 V to be considered a "1" and anything below -1 V to be considered a

In general, you can use any encoding scheme that is convenient, but
there are industry standards to allow circuits to interoperate. In
voltage controlled logic circuits, usually a voltage lower than a
certain value Vil is "Low" and a voltage above a certain value Vih is
"High". "0" is usually, though not always, represented by "Low", while
"1" is represented by "High". For example, you can find the standard
voltages for various integrated circuit families at this URL:

Some logic families use a negative voltage for Vil and a positive one
for Vih, but it is more common for both voltages to be positive.

And yes, in these circuits the electron flow changes with the
voltages. If the voltage changes from positive to negative, the flow
of electrons will change from one direction to the opposite direction.
Subject: Re: WHAT is actually sent from 1 computer to another?
From: baruch60610-ga on 03 Apr 2006 05:19 PDT
The method of transmission is electrical.  The precise details are a
bit confusing.  For example, when you have a positive (or non-zero)
voltage, that means that the flow of electrons is *less* than when you
have a zero voltage.  And the electrons don't move much.  This will
drive you nuts if you think about it too much.

But your basic understanding is OK - yes, electrical signals are
generated on the pins of chips in your computer.  These signals are
carried along by wires, or sometimes by radio waves (if you're using a
wireless system), to your modem or whatever connects you to your ISP. 
The electrical signals are carried by these wires, or possibly via
radio waves to satellites, to other computers.  Along the way, the
signals may be changed in various ways, depending on where they are. 
The signals in the wires to the ISP are different from your
computer's.  Despite this, they retain the important quality of being
able to represent two distinct states, which is the essence of the
Subject: Re: WHAT is actually sent from 1 computer to another?
From: wumply-ga on 03 Apr 2006 14:21 PDT
baruch60610-ga (or anyone in case baruch doesn't see this post.)

Can I ask you WHY the flow of elecrons is less than when you have a
"0" voltage?  That fact is fascinating!
Subject: Re: WHAT is actually sent from 1 computer to another?
From: isnraju-ga on 04 Apr 2006 19:13 PDT
The concept of pulse or absence of pulse can make things easier. these
pulses can be transmitted wirelessly. further pulse group explained as
binary number or 8 based symbol bit is used   for each character and
received as such.
translations of the data from input to machine langauage and back  are
needed to make sense othis data at the other end. For this reason I
conceptualise the data as pulses and this explains the importance of
speed as expressed in Giga Hertz and data transfer expressed in bits
per second makes easier for me to understand.
Subject: Re: WHAT is actually sent from 1 computer to another?
From: kottekoe-ga on 04 Apr 2006 20:14 PDT
But the bits may or may not be encoded as pulses. For example a very
common encoding scheme is to use positive and negative transitions to
encode the bit stream. In this case a long string of zeros (or ones,
for that matter) can be a constant voltage that is either high or low.

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