[Bob Myers]

"Floyd L. Davidson" wrote in message
...
It wasn't analog until you ran it through an analog amplifier.

More nonsense.

Again, the ONLY definitions of "analog" and "digital"
which make any sense treat these as distinctions in
the form of information encoding being used. If I
run EITHER a "digital" or "analog" signal through an
amplifier, what comes out can still be interpreted (the
information recovered from the signal) ONLY if the
encoding intent is understood and the proper decoding
applied.

A serial stream of digital data still makes sense, whether
the amplitude assigned to the "1" or "true" state is
0.1V, 1V, 10V, or 100 kV. But it makes sense
ONLY when interpreted AS a serial stream of bits.

Similarly, an analog representation of, say, video makes
sense only if interpreted AS "analog". No matter how
"digital-ish" it might look, if you try to interpret THIS
signal as a "digital" stream, you'll get gibberish.

Floyd, you would be well advised to stop treating your
"definitions" as though they were somehow handed
down by God, and instead try to employ arguments
that are actually based in something sensible.

The NTIA is an authority, and MilStd specifications are
also authoritative. That is the reason I cited them.
And the *fact* is that you have not and cannot cite any
authoritative standards body that does not agree with
them.

Neither of these - and for that matter, NO standards body
- is an Infallible Source of Absolute Truth, and no standard
should be looked at as a substitute for good ol' basic
theory and experimentation. This is the fundamental flaw
with any argument "from authority": wrong is wrong, no matter
who writes it down on a piece of paper. God knows I've
spent way more than enough time in my career working
with various standards organizations (in fact, I am currently
chairing one fairly well-known such group), including both
"industry" and "government" efforts, and I can tell you from
long and painful experience that simply because something
appears in a standards document does not make it correct.
With the right people paying close attention, these documents
can often turn out pretty darn good - but they should NEVER
EVER be used as a substitute for some actual thought and
understanding of the subject matter at hand.

Bob M.

[Arny Krueger]

"Bob Myers" wrote in message
...

"Floyd L. Davidson" wrote in message
...


If you quantize the magnitude, it is digital. That is
by definition.
No, you haven't. You merely have a signal at a set of discrete levels.

Sheesh! That *is*, by definition a digital signal.

Really? Suppose I show you an oscilloscope screen which
is displaying a single line of video, which happens to be
carrying an 8-level gray-scale pattern. It clearly shows
a set of discrete levels.

Well it shows what was once a set of discrete levels. Since it is now in the
analog domain, there will be rise time, overshoot, tilt, simple inaccuracy,
and etc. .

Further, since this video happened
to be created by a D/A converter with only three bits at
the input (our video generator was built on the cheap!), those
are the ONLY levels this signal may exhibit. Is this a
"digital" signal?

It's an analog signal that represents something that was once quantized.

Bull**** son. Look it up. I've provided you with
quotes from an authoritative reference, twice now. You
don't have to take my word for it, that *is* the agreed
technical definition of the term.

The definitions are fine, it is the misapplication of them that sticks.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...
The signal can be reconverted to an
analogue one later by a D to A.

It's best to call that a quasi-analog signal...

Why? What does that mean, EXACTLY, that
isn't already conveyed (and conveyed more accurately)
by other, more appropriate terms? What additional
information does this "quasi-analog" nonsense bring
to the party?

Bob M.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...

It is by definition. You can stand there and deny it all
you like, but that just makes *you* look damned silly.

I've cited impeccable and authoritative sources. You have not
and cannnot cite anything that supports your opinion.

Well, no, he's cited nothing but evidence and reason.
I suppose those are ignorable to anyone who treats
mere "definitions" as Holy Writ, but the rest of us somehow
find them helpful.

Again, I can cite equally acceptable and peer-reviewed
sources which use EXACTLY the "definitions" and
interpretation of these terms that Don and I and others
are using here. Do you really think this sort of think should
be decided by "battling authorities"?

Tell you what - you present an argument that ISN'T
based on an appeal to an authority, one which shows how
your notions make rational sense, and I will in turn show
you said "authorities" on the other side.

Bob M.

[Don Bowey]

On 8/21/07 7:19 AM, in article , "Floyd L.
Davidson" wrote:

Don Bowey wrote:
On 8/20/07 10:31 PM, in article , "Floyd L.
Davidson" wrote:

There simply are no such things as "analog repeaters"
on local telephone loops.

Since when?

Oh, perhaps 1950, maybe a few as late as 1960 or so...

Do you know of any telco that actually uses them today?

If a loop is long enough, and there is no pair-gain facility available, it
gets an "E" type repeater. If that isn't an analog repeater nothing is.

Of course I suppose it is possible they are still being
used where *you* live. But I don't know of any telco in
all of Alaska that has used an E repeater in the last 30-40
years. In particular, in the last 10-20 years that would
be totally unacceptable.

I didn't leave my telco job until the end of 94. At which times they were
still in use, but there was talk of using gain within the switching
machines. It wouldn't surprise me if that is being done now, being a simple
process. In any case, there are loops that require gain to meet minimum
requirements. Also, we had a tariff that provided additional gain (for a
price) where feasible.

My concerns were not just for where "I lived." I was on the Transmission
Engineering staff, and we had 14 states with which to be concerned.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...
You don't appear to understand that the limited set of values makes
it digital, by definition. PERIOD.

More argument from authority. Yawn.

Bob M.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...

Wouldn't this make the output of a D/A converter digital by definition?

It is in fact! It's a digital PAM signal. Indeed, v.90 modems
make use of it.

That's funny, so do the analog inputs of a PC monitor.
Ya just gotta wonder - how do they KNOW? :-)

However, just as you can convert an analog signal to digital, you
can indeed convert digital to analog. One method is to produce a
digital PAM signal and run it through an analog channel.

Floyd, help me out here - is a length of coax an "analog
channel" or a "digital channel"? Mine don't seem to be
labelled....

Bob M.

[Don Bowey]

On 8/21/07 8:02 AM, in article ,
"Jerry Avins" wrote:

Arny Krueger wrote:

...

Yet another *eggspurt* who has never looked at the output of a good DAC with
a scope.

Scope? SCOPE? isn't that an analog device? True digital work is don with
pencil, paper, and calculator. Theory rules!

Jerry

Since I see no smiley face to let us know you are jesting, I have to believe
you really mean it. In which case I have to believe you aren't as bright as
you were sounding. A final test of applied theory is..... Does it work as
intended? Where's my scope?

[Bob Myers]

"Floyd L. Davidson" wrote in message
...
That is, since you seem unable to grasp or investigate
it, the web site of the National Telecommunications and
Information Administration, a part of the US Federal
Department of Commerce, in Boulder Colorado. Which is
to say they are next door to and under that same
management as the NIST (the National Institute of
Standards and Technology), and NOAA (National Oceanic
and Atmospheric Administration) which you may also have
heard of...

Or, to put it another way, you will not find anywhere in
the world a valid definition that disagrees with that
one. If yours is not in agreement, you are *wrong*.

And here, kids, we see the entire heart and soul of
Floyd's argument. "My definitions are correct, because
they come from a source that I considered to be correct.
Any that aren't in agreement with these definition are
wrong, since they aren't what I consider correct."

Could it possibly GET any more circular than that?

By the way, NIST is just up the road from me: I've
contributed to (and corrected) several standards that
NIST personnel were developing. None of those people,
by the way, showed any evidence of halos or made any
claims of infallibility.

But by Gawd, Floyd will trust them implicitly, because,
after all, they're the GUMMINT!!!!!!

Logically you are walking the plank. Such technical
definitions have nothing to do with logic.

At least in your case, this is obvious.

It is an
arbitrary decision that it means this or it means that.
If we all agree on the arbitrary decision then we have a
standard, and we can use it knowing that others will
understand what it means.

Hardly arbitrary. Floyd, have you ever done ANY
standards work at all? Erroneous definitions in such
standards tend to stand until someone walks in to the
committee meetings, notices the problem, and makes
a compelling *logical* argument as to what the problem
is and how to correct it. Then it gets cleaned up in
the next revision. This does NOT mean that the older
revision was correct up until the point of change, you
know...

Bob M.

[Don Bowey]

On 8/21/07 8:36 AM, in article , "Floyd L.
Davidson" wrote:

Jerry Avins wrote:
Arny Krueger wrote:

...

Yet another *eggspurt* who has never looked at the
output of a good DAC with a scope.

Scope? SCOPE? isn't that an analog device? True digital
work is don with pencil, paper, and calculator. Theory
rules!

And you, like Arny, probably have no idea what you'd
see on a decent scope anyway.

I'd like Arny to explain how he can look at a scope and
tell if a single cycle of a sine wave is an analog signal
representing one cylce of a pure tone, or is just a digital
signal that represents 8000 different bytes of data from
a digital image.

At this point I need to say "who cares how it was generated?" It sure won't
need to be passed through any analog channel to make it analog. It is
analog by the time it gets off the board that generating it.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...


No I'm not. Let me explain with an example. Suppose I have a ramp that
changes smoothly from 0 to 1 volt. Now I quantize it in steps of 0.1
volts. I now have a staircase that rises in 0.1V steps from 0 to 1
volt.

You just digitized it. You can no longer have a value of 0.15 volts.

You can't have a value of 0.15 volts, but it's still an
"analog" signal and may be interpreted as such. Consider
the example of a gray-scale-bar pattern in an ANALOG
video system, mentioned earlier. The levels of the video
signal are ANALOGOUS to the desired luminance level,
and that's all it takes to be "analog."

No. By definition it is not. With an analogue signal you have
(technically) an infinite number of values between an input of
0.1 and 0.2. With digital you do not.

Well, by Definitions According To Floyd it's not, but
by any rational thought process Don is precisely right.
And there can never be an "inifinite" number of values
available in any signal, digital OR analog, per the
Gospel According To St. Shannon.

Digital doesn't mean numbers, it means discrete values.

Seems like they would've called it "quantized," then,
rather than using a term which contained the root word
"digit" within it. Oh, wait - people DO use "quantized"
whenever THAT word is applicable. Guess you must
be confusing the two, huh?

Bob M.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...


What you need to get straight is that it is not *my*
definition. It is the *standard* technical definition
recognized by virtually *every* standards organization.

Really? Then I shouldn't be able to find any standards
organizations which use a conflicting definition, right?

That is a logical fallacy on your part. An "argument
from authority" has great weight if it is valid. To
be valid it must pass three tests:

1) The authority cited must actually be an authority.
2) All authorities must agree on the topic.
3) The authority cannot be misquoted, taken out of
context, or be joking.

But ANY argument from authority always takes a back
seat to an argument from evidence and reason, since
those arguments directly undermine item (1) above.
Prior to the very late 19th century, all "authorities"
could be quoted as saying that it was impossible to
create a heavier-than-air flying machine. They were
all wrong. There is a nearly-endless supply of simlar
examples.

Clearly citing the NTIA and MilStd definition is indeed
a *very* strong appeal to authority, and no mere opinion
can even come close to invalidating it.

Well, it's very strong, I suppose, if you're impressed by
something simply being an NTIA or MIL standard;
if you've actually seen such things being put together,
you tend to lose a lot of reverence for them, and
certainly would never consider them to be infallible.
Standards also have a tendency to enshrine common
but erroneous thoughts, simply because they ARE
common and no one stops to question them before
they get put into the standard, simply BECAUSE
"everyone knows this" or "everyone says it."
Arguments from authority have a nasty habit of
breeeding more "authority," through cycles of
repeated reference to incorrect notions.

You know one way to be absolutely positive that your
logic is not good is to do a reality check and find that
the answer you have is wrong. It this case that is very
easy to do, which is why *standard* definitions are
quoted from authoritative sources. If you disagree,
then clearly you *don't* have the logic right!

You sound exactly as one who would be arguing, in
early 1904, against investing in those crazy Wright
brothers, since it's clear RIGHT HERE IN THIS
TEXT that a flying machine is impossible! Anyone
who says or even, God forbid, demonstrates otherwise
clearly MUST be wrong. (This is the Reality Must
Always Change to Conform To Established Thought
position.)

However, if you like, I can also point to several
references which support the definition that Don and I (and

So cite even one such valid reference! (You *cannot*,
because there are none.)

(And recognize that if you think you have one, then
there is one of two things clearly true: Either 1) you
do not understand that the other definition is not
actually different, or 2) your reference is not a valid
one.)

Once again: "MY references are right, because they
agree with me - YOURS simply MUST be wrong, because
they don't!" What a wonderfully circular form of
argumentation you have there!

You are not a valid reference. You don't even come
close to being equal to the NTIA.

Floyd, who do you think makes up the NTIA or
any other standards body? Gods who have come
down from Olympus?

Bob M.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...
Floating point is analog, integer is digital.

This will be news to anyone designing floating-point processors....

Bob M.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...
You can repeat that all you like, but you are wrong
every time you do.

By *definition* it is a digital signal.

quantization:
A process in which the continuous range of values
of an analog signal is sampled and divided into
nonoverlapping (but not necessarily equal)
subranges, and a discrete, unique value is assigned
to each subrange.

Funny, I don't see the word "digital" in there. Perhaps
you could point it out? No one is arguing that
"quantized" does not mean the above - but you seem
to be arguing that "quantized" is precisely equivalent
to "digital," while none of the definitions you provide
say that.

If you do not stay with standard definitions it is
impossible to discuss anything rationally.

Yes, you have made that quite evident.


QUANTIZATION:
A process in which the continuous range of values
of an analog signal is sampled and divided into
nonoverlapping (but not necessarily equal)
subranges, and *a* *discrete*, *unique* *value* *is*
*assigned* to each subrange.

Yes, you said that again; you repeat it as though it
were a mantra that would somehow make your particular
odd misunderstandings correct. Again, please show me
the word "digital" IN THIS DEFINITION.


No matter how dense you want to be about it, that
government "expert" happens to be right. And you cannot
find *any* expert that will disagree.

No one that you will accept as an "expert," at least,
since apparently "by definition," an "expert" is someone
who agrees with your position, and no one who disagrees
could possibly be an "expert." Or can you please tell
us some OTHER criteria that you would use to judge
"expertise," so that we can search for "experts" that
you would find authoritative?

That is the
*standard* definition, and virtually *everyone* agrees
that it is correct.

Since there are numerous respondants in this thread
who apparently do NOT agree with your claim that
this is the "standard definition," that statement is
prima facie incorrect.

Bob M.

[Don Bowey]

On 8/20/07 11:30 PM, in article , "Floyd L.
Davidson" wrote:

Don Bowey wrote:
On 8/20/07 10:19 PM, in article , "Floyd L.
Davidson" wrote:

Don Bowey wrote:
On 8/20/07 8:14 PM, in article , "Floyd L.
Davidson" wrote:

Of course if you then run that digital PAM signal through virtually
any analog channel, it no longer has a limited set of values...

Including a two foot piece of cable, or two inches with a small cap.

Nope. It would take a fair sized cap.

Keep in mind that that is *exactly* what a V.90 modem puts on a
regular twisted pair telephone cable, and it works just fine for
a couple miles at least, sometimes even much farther.

And that signal is digital, and is processed as a digital signal
by the receiving modem.

Digital data CSUs and T1 transmitter line signals are digital and look
similar to distorted square waves. An all 1's signal looks like a
distorted
sinewave .

Your point is? (Besides the poor description? They
don't look like distorted square waves. The look like
only slightly distorted sine waves!)

Have you looked at a DSX-1 envelope lately?

Yes. I've got the specs right here! :-) Literally, I have
had a graph on my web site for several years now that I drew up
to illustrate something I wrote once upon a time

http://www.apaflo.com/floyd_davidson/t1pulse.jpg

(snip)

The pulse for which you provided the link, is not DSX-1, because it will not
fit within the DSX-1 envelope.

I posted the DSX-1 template, and a representative pulse within it (MS Word),
on a.b.s.e. The pulse shown was from equipment that generated the pulse
using an analog method. As you can see from the envelope, other pulses,
specifically, those generated digitally, could be much more "square" if
given enough processing time.

Numeric points for plotting the template to a spreadsheet are available if
anyone wants them, but I will be away until next Saturday.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...
(Again, that is
the nature of arbitrary definitions, this time of what
"encode" and "modulate" mean.)

Definitions are arbitrary only to those who don't
truly understand them.

Bob M.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...

Your opinion of standard definitions is worthless.


....because it disagree's with Floyd's opinion, and
Floyd has somehow been granted Infallibility by the
Gods of Technology.

Or does that only apply when you are wearing the
big white hat and formally speaking ex cathedra?

Bob M.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...

Again, not really true. Quantized is necessarily
digitized.

Why? And please, for a change, try to cite a REASON,
not merely a definition. After all, if you have the level
of understanding of this topic that you implicitly claim,
you should easily be able to do that.

Bob M.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...
Look up the definition of "quantization" again. It simply
makes no difference. If an analog signal is quantized, the
result is a digital signal. That is by definition, and you
cannot escape that with mumbo-jumbo and faulty logic.

But of course, you haven't yet even posted a definition
which says that, let alone provided any reasoning which
would support such a definition.

Bob M.

[Bob Myers]

"Floyd L. Davidson" wrote in message
...
Note, for example, that an analog current is quantized in units
of the charge on the electron.

No, in fact it is not. Electrons do not necessarily all move
at the same speed...

Ummmm - now you have a problem with the definition
of the units used to quantify current? An Ampere (the
standard unit of current) is defined as 1 Coulomb of charge
passing a given point per second, and the Coulomb is most definitely
defined in terms of the fundamental unit of charge (which equals
the magnitude of charge on a single electron). Nothing in this
requires all the electrons to be moving at the same speed,
any more than a flow of 10 gallons/hour of water requires that
I move each ounce of water at the same rate.

Geeze, Floyd, which is it? Either definitions are important,
or they're not.

Bob M.

[isw]

In article ,
(Floyd L. Davidson) wrote:

You don't appear to understand that the limited set of values makes
it digital, by definition. PERIOD.

So, does that make quantum physics "digital"?

Isaac

[Jerry Avins]

Floyd L. Davidson wrote:
Jerry Avins wrote:
Arny Krueger wrote:

...

Yet another *eggspurt* who has never looked at the
output of a good DAC with a scope.
Scope? SCOPE? isn't that an analog device? True digital
work is don with pencil, paper, and calculator. Theory
rules!

And you, like Arny, probably have no idea what you'd
see on a decent scope anyway.

I'd like Arny to explain how he can look at a scope and
tell if a single cycle of a sine wave is an analog signal
representing one cylce of a pure tone, or is just a digital
signal that represents 8000 different bytes of data from
a digital image.

If it comes down a wire, it's analog. You wrote that yourself at one point.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Jerry Avins]

Floyd L. Davidson wrote:
Jerry Avins wrote:
Floyd L. Davidson wrote:
(Don Pearce) wrote:
...

You have cited a source that is describing something else. It is a
Bull**** Don, that is abjectly stupid to claim.

source that you claim is authoritative and impeccable. Kindly go and
read what it has to say on the Nyquist rate and come back and repeat
that claim without blushing. Actually I'm betting you won't blush
because you won't understand the problem.
Nyquist rate:
The reciprocal of the Nyquist interval, i.e., the
minimum theoretical sampling rate that fully
describes a given signal, i.e., enables its
faithful reconstruction from the samples. Note:
The actual sampling rate required to reconstruct
the original signal will be somewhat higher than
the Nyquist rate, because of quantization errors
introduced by the sampling process.
So, quantization error is the reason one has to sample
faster than the Nyquist rate! If you believe that,
there's a bridge I want to sell you.

If you don't understand what they said, you probably do
have a bridge that somebody sold you...

Maybe I didn't understand. Please clarify
"The actual sampling rate required to reconstruct the original signal
will be somewhat higher than the Nyquist rate,
*because of quantization errors introduced by the sampling process"*
(emphasis added).

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Jerry Avins]

Don Bowey wrote:
On 8/21/07 8:02 AM, in article ,
"Jerry Avins" wrote:

Arny Krueger wrote:

...

Yet another *eggspurt* who has never looked at the output of a good DAC with
a scope.
Scope? SCOPE? isn't that an analog device? True digital work is don with
pencil, paper, and calculator. Theory rules!

Jerry

Since I see no smiley face to let us know you are jesting, I have to believe
you really mean it. In which case I have to believe you aren't as bright as
you were sounding. A final test of applied theory is..... Does it work as
intended? Where's my scope?

Sorry, Don. I thought the sarcasm would be obvious.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Floyd L. Davidson]

"Arny Krueger" wrote:
"Floyd L. Davidson" wrote in message
...
Jerry Avins wrote:
Arny Krueger wrote:

...

Yet another *eggspurt* who has never looked at the
output of a good DAC with a scope.

Scope? SCOPE? isn't that an analog device? True digital
work is don with pencil, paper, and calculator. Theory
rules!

And you, like Arny, probably have no idea what you'd
see on a decent scope anyway.

(1) A decent scope gives a pretty close approximation of what theory
predicts.

True. Theory predicts that you cannot look at a scope
and tell what kind of information, digital or analog, is
carried by a signal. So one wonders why you want to talk
about scopes.

(2) I was probably working with decent scopes before you were born.

Nobody made a "decent" scope for several years after I
was born.

Bringing up the distraction of looking at such signals
with a scope clearly indicates that you do not
understand it. You *cannot* distinguish between digital
and analog signals with a scope. (See below, for a very
good example of why that is true.)

I'd like Arny to explain how he can look at a scope and
tell if a single cycle of a sine wave is an analog signal
representing one cylce of a pure tone, or is just a digital
signal that represents 8000 different bytes of data from
a digital image.

I've seen both kinds of data many times. Imaging data almost never looks
like sine waves.

It *commonly* does. Every time anyone fires up a v.90
modem and downloads *anything*, the waveform on the
signal from the telco to the subscriber's v.90 modem
looks like sine waves. That is true whether it is
imaging data, text, voice, or whatever else you can
think of.

But in fact those "sine waves" are as much as 8000 bytes
per second digital signaling.

And if you put your scope on the line and look at them,
and then hang up the phone and make a voice call, you
will not be able to see *any* difference between the
analog voice signal and the v.90 protocol digital
signal!

The reason is because there absolutely is no difference
at all. Both signals are generated in exactly the same
way by the exact same CODEC in the line card at the
telco. They necessarily will look identical on a scope.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Scott Seidman]

"Bob Myers" wrote in news:faf4co$co5$1
@usenet01.boi.hp.com:


Really? Then I shouldn't be able to find any standards
organizations which use a conflicting definition, right?


The nicest thing about standards is that there are so many from which to
choose.


--
Scott
Reverse name to reply

[Floyd L. Davidson]

"Bob Myers" wrote:
"Floyd L. Davidson" wrote in message
...


"Analog" != "continuous," even though most commonly
"analog" signals are also continuous in nature.

Analog signals are by *definition* continous.

Nonsense. You don't believe it is possible to sample
an "analog" signal and have it remain analog?

I didn't say that an analog signal is always present. I
said the value representation is by definition
continuous.

If you cannot understand these simple things without it
being spelled out in detail what they mean...

You have misunderstood what that means though. The
analog value of a signal is continuous,

Well, THAT certainly makes it clearer....

And of course you had no idea until now that that is
what we've always been talking about, right?

The fact that this sort of trivial detail has to be
explained to you certainly indicates just how uninformed
you are on this topic. You should not be arguing with
anyone about it, but asking questions and learning.

Since you seem to be so hung up on definitions, Floyd,
try this one on for size:

Continuous: unchanged or uninterrupted: continuing
without changing, stopping, or being interrupted in space
or time.

Now apply that to the value of an analog signal, and you
too can have a good understanding of the definitions
used to distinguish between analog and digital.

Please note that a non-existent signal cannot be either
analog or digital. Hence when you try to weasel out of
valid definitions for a signal by claiming that pulsed
samples are not continuous, it might seem cute to you,
but it is trivially childish.

The definition does not say that the signal's
*existence* is continuous, it says that the *value* of
the signal is continuous for analog while digital has a
finite set of discrete values.

Note that this does not say anything at all about the range
of possible values being "continuous" (which is what you
seem to be trying to say in the above).

True, it doesn't say anything at all about the
definitions of digital and analog, so one wonders why
you would bring up such a childish and trivial attempt
at obfuscation. Other than the obvious fact that it has
finally dawned on you that the definitions provided are
in fact rigorously correct...

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Floyd L. Davidson]

"Arny Krueger" wrote:
"Floyd L. Davidson" wrote:

Regardless, the idea that you think looking at a signal
with a scope will tell you if it is digital or analog
suggests that you weren't paying attention when you
studied basic signal theory, if you ever did.

I aced "Signals And Systems Analysis" and placed high in "Linear Stochastic
Optimal Control" - probably the heaviest signals trips I ever took.

Then you *should* know that you cannot look at signals
on a scope and tell if they are analog or digital.

How do you explain the conflict between what you claim
your education is and the practical level your previous
post demonstrated?

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Floyd L. Davidson]

"Bob Myers" wrote:
"Floyd L. Davidson" wrote in message
...


If you quantize the magnitude, it is digital. That is
by definition.
No, you haven't. You merely have a signal at a set of discrete levels.

Sheesh! That *is*, by definition a digital signal.

Really?

Do you need the definitions repeated? If the values are
discrete and from a finite set, that is defined as digital.

Crawl into a corner and deny standard definition of terms
if you like, but it means that nothing you say about the
topic is credible.

Suppose I show you an oscilloscope screen which
is displaying a single line of video, which happens to be
carrying an 8-level gray-scale pattern. It clearly shows
a set of discrete levels.

It shows no such thing. You cannot tell from looking at
it how many levels it could possibly have. You can't
actually tell (just from looking at it) how many levels
it has at any given instant.

The scope simply does not tell you that sort of
information. It only shows you what currently exists,
and over a period of time you can (perhaps) get an idea
of at least some of the possible range of variations.
But you *cannot* tell if the variations are or are not
discrete or continuous.

Only if you already know absolutely what the format is,
can you determine what part of the format you are
seeing.

Further, since this video happened
to be created by a D/A converter with only three bits at
the input (our video generator was built on the cheap!), those
are the ONLY levels this signal may exhibit. Is this a
"digital" signal?

You have said nothing that makes it necessary one or the
other.

Bull**** son. Look it up. I've provided you with
quotes from an authoritative reference, twice now. You
don't have to take my word for it, that *is* the agreed
technical definition of the term.

Ah, Floyd - argument from authority again, huh?

Ah, Bob... that is very clearly a *valid* appeal to
authority. The quotes are indeed from an expert,
virtually *all* experts agree with what that
particular one said, and the quotes were in context and
meant to be what I claim they are. Look it up in any
reference work on logic, and you'll find that is
precisely what makes such an argument valid.

You, on the other hand, have a totally worthless
opinion, with nothing at all to support it. And that's
why you continue to make such gross errors!

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Floyd L. Davidson]

"Arny Krueger" wrote:
"Bob Myers" wrote in message
...

"Floyd L. Davidson" wrote in message
...


If you quantize the magnitude, it is digital. That is
by definition.
No, you haven't. You merely have a signal at a set of discrete levels.

Sheesh! That *is*, by definition a digital signal.

Really? Suppose I show you an oscilloscope screen which
is displaying a single line of video, which happens to be
carrying an 8-level gray-scale pattern. It clearly shows
a set of discrete levels.

Well it shows what was once a set of discrete levels. Since it is now in the
analog domain, there will be rise time, overshoot, tilt, simple inaccuracy,
and etc. .

That has no relevance to whether it represents a discrete set
of values.

Further, since this video happened
to be created by a D/A converter with only three bits at
the input (our video generator was built on the cheap!), those
are the ONLY levels this signal may exhibit. Is this a
"digital" signal?

It's an analog signal that represents something that was once quantized.

It could also be a digital signal. You simply cannot
tell from looking at a scope.

Bull**** son. Look it up. I've provided you with
quotes from an authoritative reference, twice now. You
don't have to take my word for it, that *is* the agreed
technical definition of the term.

The definitions are fine, it is the misapplication of them that sticks.

Oh, are we back to the idea that the NTIA had never heard of
PCM when they came up with those definitions?

In fact, *you* are not able to apply them, as is obvious from
what you said above.


--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Piergiorgio Sartor]

Floyd L. Davidson wrote:

No, you haven't. You merely have a signal at a set of discrete levels.

Sheesh! That *is*, by definition a digital signal.

Maybe you should go back to look at the root of the word "analogue".
It is the same as "analogy".
And, usually, it means that a physical entity is represented (by
analogy) by an other physical entity.
For example, a mercury thermometer uses the "length", a physical
entity, to represent the "temperature", an other physical entity.
The analogy is "inches" ("millimeters") to "degrees".
A pressure gauge uses "angle degrees" as analogy for "pascal".
So it does an analog volt meter.

On the other side we have digital, where a number is used to
represent a physical entity. And this is a just plain number, so
the signal represented has no physical energy, only statistical.
A digital thermometer shows directly the temperature as a number.

All this has nothing to do with sampled, discreet, quantized,
continuous an so on.

Sometimes the analogy is one to one (length for length, for example),
but the concept is the same.

bye,

--

piergiorgio

[Bob Myers]

"Floyd L. Davidson" wrote in message
...
Except that "absence of noise" is a condition which
doesn't exist, even in theory.

Apparenlty Claude Shannon didn't agree with you on that.

And apparently you don't understand what was meant in
the above.

It is theoretically impossible for any real-world communications
channel to be noise-free or possessed of infinite bandwidth.
Do you disagree with this statement? If so, please show the
error.

This does not prevent a noise-free channel from being IMAGINED,
and used as the basis for a mathematical analysis, which is
what Shannon did. But Shannon most definitely did NOT
expect any such thing to be realized, and fully understood
why it could not be.

Have you even read Shannon's paper? In section V (27),
Shannon makes virtually the same statement I gave earlier
re the notion of "infinite" levels:

"This means that to transmit the output of a continuous
source with *exact recovery* [emphasis Shannon's]
at the receiving point requires, in general, a channel of
infinite capacity (in bits per second). Since ordinarily
channels have a certain amount of noise, and therefore
a finite capacity, exact transmission is impossible."

Gee, here's another puzzler for you - throughout his
paper, Shannon discusses channel capacity in terms of
"bits per second." Does this mean that his work is
applicable only to digital systems? If not, why not?

Bob M.

[Bob Myers]

"Radium" wrote in message
oups.com...
On Aug 20, 8:47 am, "Bob Myers" wrote:

You can also
reduce the temporal frequency in the case of motion video.

That's what I was talking about. Reducing the temporal frequency of
the video w/out low-pass filtering or increasing the length of the
movie.

And THAT is simply using a lower frame rate in the first
place. No "filtering" involved, per se, but it can have some
undesired results in terms of the portrayal of motion, etc..

Bob M.

[Floyd L. Davidson]

"Arny Krueger" wrote:
"Floyd L. Davidson" wrote:
"Arny Krueger" wrote:
"Floyd L. Davidson" wrote:

Well, analog amplifiers generally have upper limits for frequencies
that they will pass.

Actually, they all do.

However, if the upper limit is more than 2 or 3 times
higher than the frequency spectrum of the signal, in
effect they don't.

Nope, the phase shift is appreciable down to Fc/10. Ever hear of Bode plots?

"Appreciable" is not specific... The point is that in
practical applications there are few effects at Fc/2
which are unreasonable. Measurable? Sure, but so what.

For example... A typical voice channel provided by the
telecommunications industry is often stated as a 4Khz
wide channel. In fact of course it is not. The lower
limit is determined by high pass filters designed to
reduce 60Hz power line interference. Cutoff filters are
usually at about 80 Hz for that. The high end is
limited in digital systems by the need to avoid aliasing
of frequencies above 4000Hz, so the LP filters generally
have a cutoff between 3750 and 3850. Essentially that
provides a 80-3750Hz channel, maximu.

The industry only guarantees that they will provide
400-2800 Hz of bandwith over the Public Switched
Telephone Network. Much of the reason for that is
that phase shifts and envelop delay at frequencies
from 3000 to 3750 are sometimes (but not always) high
enough to be a problem (which would require special
conditioning to correct for).

You are saying the effects are "appreciable" down to
375 Hz, which means the _entire_ 400-2800Hz bandwidth
is suffers "appreciable" effects.

It can be measured, but it does *not* cause appreciable
effects.

The point is we are *not* talking about wideband
amplifiers and narrow band signals, we are talking about
practical applications where the two are very closely
matched.

Most digital audio is brick walled at 0.95 * Fs/2 or about 21 KHz. Most
power amps are pretty flat up to about 50 KHz.

So, as I've stated... your example shows that the
filters are placed at 0.95 times the maximum possible
frequency that can traverse the channel. And those
filters are on the *input* to the channel.

The fact that the power amp, the last part active of the
system, actually has a greater bandwidth (even then,
only 2x), is insignificant. What about the bandwidth of
the output stages of the D to A converter... That is
where it makes the most difference in regard to
conversion of digital to quasi-analog to analog without
appreciable artifacts. But secondarily, the speakers
are also an important part of the overall channel... and
ultimately the point at which a digital signal is
absolutely converted to analog (perhaps artifacts and
all).

There's all sorts of phase distortion which
occurs when the frequency response drops off.

Usually, its pretty simple.

Sure it is... That's why there are complete books
published on what happens?

For people who don't already know?

You said it was simple. Apparently you should read up
on the topic.

That may not affect
your ability to understand speech that is amplified through such
a device, but it does have a really significant effect on other
devices. For example, it makes an analog signal out of a digital
PAM signal.

Nope, the output of good DAC is generally even more severely band-limited

Limited by the sampling rate.

Well, by the brick wall filter which is usually set as stated above.

The brick wall filtering is on the channel *input*, to
prevent aliasing. It does not limit what could show up
on the output, as if it were not there the frequencies
that it removes would be folded at the output anyway.
The absolute upper limit (at which point it generates
100 percent distortion) is Fs/2, for input bandwidth.

than that of a good amplifier. That's why they call the filtering in DACs
"brick wall filters".

That is to prevent aliasing though,

DACs can't alias. Only ADCs can alias. Improperly filtered DACs may produce
images.

Okay... if you want to limit this to separating the ADC
from the DAC, the DAC doesn't have the brick wall
filter, the ADC does.

How do you get an image out of a DAC, if it wasn't
produced at the ADC?

Improperly filtered channel output might have artifacts
from the sampling though, but no HP output filtering is
necessary to remove any signal resulting from the input
signal.

and is actually a
higher frequency cutoff than what is required to affect
the resulting output. And they are used on the *input*,
not on the output.

The input side of a digital system is called an ADC, not a DAC as you just
said.

They are both part of a "digital channel", and *that* is
what I am talking about. Nothing else makes sense in
this context.

--
Floyd L. Davidson http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

[Don Pearce]

On Tue, 21 Aug 2007 07:00:57 -0800, (Floyd L.
Davidson) wrote:

Nyquist's theorem: A theorem, developed by H. Nyquist, which states
that an analog signal waveform may be uniquely reconstructed, without
error, from samples taken at equal time intervals. The sampling rate
must be equal to, or greater than, twice the highest frequency
component in the analog signal. Synonym sampling theorem.

Go ahead and defend.

Claude Shannon proved it mathematically in the late
1940's.

You are free to dispute Shannon...

I don't dispute Shannon and he didn't write the above. Show me how
sampling at a rate equal to twice the highest frequency works. It is
there quite explicitly. Could you not even spot that? The entire
clause "must be equal to" is incorrect.

But I forget, this is authoritative so it must be right. Shame Shannon
got it wrong all those years ago, isn't it?

d

--
Pearce Consulting
http://www.pearce.uk.com

[Bob Myers]

"Radium" wrote in message
ps.com...
Actually I don't want other parts to be unchanged. What I would like
is the temporal frequencies [of all parts of the video] to be
decreased but without decreasing the speed of the video signal.

And here's where you need to be clearer, and very likely
do some more thinking about what you're after - exactly
what do you mean by "speed" of the video signal?

Bob M.

[Arny Krueger]

"Floyd L. Davidson" wrote in message
...
(Don Pearce) wrote:
On Mon, 20 Aug 2007 12:42:38 -0400, Jerry Avins wrote:

Don Pearce wrote:

... If you are doing digital signal processing, you are
doing arithmetic on the numbers that come out of an AtoD converter.
You can't do that with some voltage levels out of a quantizer.

Transversal and recursive filters and correlators have been built that
operate on unquantized samples. Fourier transforms have been "computed"
with lenses. Do you remember the early days of side-looking radar?

Quantization isn't important. If you don't quantize all it means is
that you are dealing with floating point rather than integer numbers.
Still digital of course. I can't think of any floating point ADC's off
hand, of course.

Floating point is analog, integer is digital.

?????????????????????

[Don Pearce]

On Tue, 21 Aug 2007 07:06:03 -0800, (Floyd L.
Davidson) wrote:

(Don Pearce) wrote:
On Mon, 20 Aug 2007 22:36:22 -0800, (Floyd L.
Davidson) wrote:

(Don Pearce) wrote:
On Mon, 20 Aug 2007 16:35:14 -0800, (Floyd L.
Davidson) wrote:


A "quantized analogue signal" is digital by definition.


No, you haven't. You merely have a signal at a set of discrete levels.

Sheesh! That *is*, by definition a digital signal.

If you put that signal through an analogue amplifier, it will be
amplified. That makes it an analogue signal.

It wasn't analog until you ran it through an analog amplifier.

Really? Suppose that having put it through the amplifier (somehow
converting it to an analogue signal, it now appears), I now put it
through an attenuator, dropping it back to its original size. It is
now identical to what went into the amplifier. Has the attenuator
converted it back to a digital signal, or is it still analogue? Think
about this carefully please. It really is at the heart of what we are
talking about.

Well, analog amplifiers generally have upper limits for frequencies
that they will pass. There's all sorts of phase distortion which
occurs when the frequency response drops off. That may not affect
your ability to understand speech that is amplified through such
a device, but it does have a really significant effect on other
devices. For example, it makes an analog signal out of a digital
PAM signal.


Bull****. Unless of course you are claiming that all digital signals
have perfectly flat tops and vertical edges. Is that your claim,
Floyd? You are no longer waving, but drowning. Just admit you have
this all wrong and bow out with as much grace as you can manage.

Phase may not affect your ears much, but it does affect
the data. It has nothing to do with flat tops and
vertical edges, which seem to be something you can't get
around.

I know you don't understand that, but everything else seems hard
for you too.

Floyd, you have just claimed (in public!, this really is pricelessly
funny) that an amplifier is a D to A converter. I would like to know
if an attenuator is an A to D converter.

If you think about the above for awhile, you're in for a big
surprise.

All of a sudden he has no answer. Come on Floyd - it is your claim
that an amplifier is a D to A converter. Now put up or shut up. Defend
it or admit you have screwed up.

My point is that there is a lot more to a practical
amplifier than just simple gain. Sorry that you missed
the point, again.

No. You said that a signal that goes into an amplifier digital will
come out analogue. Now justify that piece of **** or go away.

d

--
Pearce Consulting
http://www.pearce.uk.com

[Arny Krueger]

"Floyd L. Davidson" wrote in message
...
"Arny Krueger" wrote:
"Floyd L. Davidson" wrote in message
...
Jerry Avins wrote:
Arny Krueger wrote:

...

Yet another *eggspurt* who has never looked at the
output of a good DAC with a scope.

Scope? SCOPE? isn't that an analog device? True digital
work is don with pencil, paper, and calculator. Theory
rules!

And you, like Arny, probably have no idea what you'd
see on a decent scope anyway.

(1) A decent scope gives a pretty close approximation of what theory
predicts.

True. Theory predicts that you cannot look at a scope
and tell what kind of information, digital or analog, is
carried by a signal. So one wonders why you want to talk
about scopes.

Not true. Theory predicts the scope pattern that various kinds of signals
will produce.

(2) I was probably working with decent scopes before you were born.

Nobody made a "decent" scope for several years after I
was born.

Yeah, sure.

Bringing up the distraction of looking at such signals
with a scope clearly indicates that you do not
understand it. You *cannot* distinguish between digital
and analog signals with a scope.

As a rule, I can. Been doing it for about half a century, more or less.

(See below, for a very good example of why that is true.)

I'd like Arny to explain how he can look at a scope and
tell if a single cycle of a sine wave is an analog signal
representing one cylce of a pure tone, or is just a digital
signal that represents 8000 different bytes of data from
a digital image.

I've seen both kinds of data many times. Imaging data almost never looks
like sine waves.

It *commonly* does. Every time anyone fires up a v.90
modem and downloads *anything*, the waveform on the
signal from the telco to the subscriber's v.90 modem
looks like sine waves.

You've picked a situation where *everything* including no data at all looks
like sine waves. What you see on a modem line is not the actual data, you
see that data modulating sine waves.

That is true whether it is
imaging data, text, voice, or whatever else you can
think of.

So what?

But in fact those "sine waves" are as much as 8000 bytes
per second digital signaling.

So what?

And if you put your scope on the line and look at them,
and then hang up the phone and make a voice call, you
will not be able to see *any* difference between the
analog voice signal and the v.90 protocol digital
signal!

So what?

The reason is because there absolutely is no difference
at all. Both signals are generated in exactly the same
way by the exact same CODEC in the line card at the
telco. They necessarily will look identical on a scope.

So what?

[Arny Krueger]

"Don Bowey" wrote in message
...
On 8/21/07 8:36 AM, in article , "Floyd L.
Davidson" wrote:

Jerry Avins wrote:
Arny Krueger wrote:

...

Yet another *eggspurt* who has never looked at the
output of a good DAC with a scope.

Scope? SCOPE? isn't that an analog device? True digital
work is don with pencil, paper, and calculator. Theory
rules!

And you, like Arny, probably have no idea what you'd
see on a decent scope anyway.

I'd like Arny to explain how he can look at a scope and
tell if a single cycle of a sine wave is an analog signal
representing one cylce of a pure tone, or is just a digital
signal that represents 8000 different bytes of data from
a digital image.

At this point I need to say "who cares how it was generated?" It sure
won't
need to be passed through any analog channel to make it analog. It is
analog by the time it gets off the board that generating it.

At some level every signal is analog. The digital nature of a signal comes
from how it is coded and decoded.