Questions about equivalents of audio/video and digital/analog.

[Arny Krueger]

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

Sure I can. If I look at a line between two V-90 modems, I can immediately
see that it is an analog line. It may be carrying audio or video, but thats
about the data that is being carried, not the signal that I'm looking at.

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

Simple - you misunderstood what I said because you can't distinguish between
a signal and that data that it may represent.

 

[Floyd L. Davidson]

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.

I'll be damned, you *finally* got *something* right!

Did you go back and actually read what I said, or did
you learn this somewhere else? Regardless, the above
supports *exactly* what I've been saying, and I do hope
that you have begun to make the connection.

After being passed through an analog amplifier, the data
has a totally different set of values than it did within
the digital system (the output of the digital system has
both sets, but once it enters an analog channel the digital
values are generally, though not always, lost), and it can
be applied to an analog transducer (such as a speaker)
with the desired effects.

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.

Exactly. It is the *information* carried that
determines what is digital and what is analog. Others
have claimed that looking at it with a scope is a way to
determine which, but that is not true. A digital signal
has discrete values (whether that is represent by 0.1v
or 100Kv) from a finite set. An analog signal has a
continuous range of values. It is the values of the
*data* that make a difference, not voltage levels, phase
shifts, or whatever.

The fact that voltage can and does get varied over a
continuous range of voltages means *nothing*; but if
that continuous range of voltages represents a finite
set of data values it is a digitial signal and if it
represents a continuous set of data values it is an
analog signal.

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.

Well, if you aren't just paroting back to me everything
I've been telling you, and now claiming it isn't what
you denied at every turn of the way!

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.

You just agreed, and stated, that they are correct. I
use them correctly, and have from the beginning of this
discussion without fail.

You keep wandering all over the map because you simply
do not understand how it applies to more than a minimal
set of circumstances, apparently.

Neither of these - and for that matter, NO standards body

In fact, those two are, for these definitions, valid
authorities. You have not and cannot come up with
anyone who is credible that does not agree with them.

- is an Infallible Source of Absolute Truth, and no standard
should be looked at as a substitute for good ol' basic
theory and experimentation.

And when you do your own homespun theorizing and come up
with *wrong* answers, it is ridiculous for you to claim
the standard definitions used by virtually everyone else
are wrong instead of you.

This is the fundamental flaw
with any argument "from authority": wrong is wrong, no matter
who writes it down on a piece of paper.

And Bob Myers is *wrong*. You can claim otherwise all
you like, but when you disagree with every authority
there is on the definitions of basic fundamental terms,
it is abject *foolishness*.

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.

That's a great deal of hand waving there Bob. You are
in fact making an invalid appeal to authority! You are
not an expert, and other experts do not agree with you.
Your logic is invalid.

Then you go on too make another basic logical mistake.
The fact that some Standards have been in error would
not suggest that all Standards are in error. You cannot
cite (nebulous and unspecified) errors in other
standards as a proof that those definitions are an
error.

 

[Floyd L. Davidson]

Well, no, he's cited nothing but evidence and reason.

He, like you, has cited *nothing*.

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"?

If you could, you would have. You can't.

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.

I am not an authority, and make no claims to being one.
It would be abjectly ridiculous for me to attempt to
present my own rationalizations for why standard
definitions are what they are. The *only* rational that
is important is that of authorities on the subject. No
me, not you.

You are asking me to act just as foolishly as you have,
and I refuse.

 

[Bob Myers]

Did you go back and actually read what I said, or did
you learn this somewhere else? Regardless, the above
supports *exactly* what I've been saying, and I do hope
that you have begun to make the connection.

I've said it all along, Floyd; if you want to see where I said
it even earlier, I could refer you to my book...

Exactly. It is the *information* carried that
determines what is digital and what is analog.

Gee, that's funny. Earlier you were claiming that
simply "quantizing" a signal was sufficient to make
something "digital." You were also talking about
"digital" and "analog" channels - so I would have to
assume, from this, that you are of the belief that
channels can somehow "know" the nature of the
information they are carrying, and thus become
"digital" or "analog" themselves.

The fact that voltage can and does get varied over a
continuous range of voltages means *nothing*; but if
that continuous range of voltages represents a finite
set of data values it is a digitial signal and if it
represents a continuous set of data values it is an
analog signal.

Oh, too bad! You were SO close to having it right, and
then your preconceived notions again got in the way.

It has NOTHING TO DO with whether the range is
continuous or not, it has EVERYTHING to do with
how the signal is to be interpreted. My monitor has an
"analog" input, which is so named because it "knows"
that if it's presented with a video signal level twice that
of this other level over here, it should produce twice
the luminance ("gamma" effects ignored for simplicity).
This has nothing to to with how many intermediate levels
there may be between these two, or even if there are
ANY intermediate levels between the two - solely with
the fact that the levels themselves are direct "analogs"
(gee, there's that word again) to the desired luminance
level.

Well, if you aren't just paroting back to me everything
I've been telling you, and now claiming it isn't what
you denied at every turn of the way!

I would love to see you show me where I denied ANY
of the above.

That's a great deal of hand waving there Bob. You are
in fact making an invalid appeal to authority! You are
not an expert, and other experts do not agree with you.

And your sole rationale for saying that I am not an
"expert" is: I disagree with you! Wow, that's an amazingly
logical position, isn't it?

Then you go on too make another basic logical mistake.
The fact that some Standards have been in error would
not suggest that all Standards are in error.

You need a course in basic logic. I did not argue that "the fact
that some standards are in error suggests that all standards
are in error." What I argued was the fact that some standards
are in error suggests that other standards may also be in error,
and cannot be assumed to be correct simply because they are
"standards."

Bob M.

 

[Bob Myers]

Sure I can. If I look at a line between two V-90 modems, I can immediately
see that it is an analog line.

OK, Arny - what are the distinguishing characteristics of
an "analog line"? Once we have determined that we have
an "analog line," does this mean that said line cannot possibly
be used to carry "digital" information? If not, then what is
the significance of designating said line to be "analog" in the
first place?

Bob M.

 

[Bob Myers]

I am not an authority, and make no claims to being one.

Then on what grounds do you judge the correctness
of the definitions you yourself reference? Are you
simply accepting them as Holy Writ because they DO
come from some body that you view as "authoritative,"
and you are incapable of making any judgement, yourself,
of their technical merit?

It would be abjectly ridiculous for me to attempt to
present my own rationalizations for why standard
definitions are what they are. The *only* rational that
is important is that of authorities on the subject. No
me, not you.

So what do you use to judge "authority" in the first
place? Because someone, at some point, told you that
"such-and-such is an authority, you can trust it/him/her/
them"? What do you do if someone ELSE points to a
different "authority" who has a conflicting position, if you
yourself are not competent to judge? You say that I
must not be an "authority" because I take a position
contrary to that of some other "authority" that you knew
about earlier - but then you also say that you yourself
have no criteria whatsoever for making such an
evaluation, OTHER than the previous "authority"?

This feels more and more like arguing with a Creationist...

Bob M.

 

[Floyd L. Davidson]

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

So you don't know of any telco that uses them today.

I assume you were also using mechanical switching there
too... ;-)

It is sort of difficult for me to imagine that sort of
environment, as Alaska was fully digital when the rest
of the country had only gone 33% digital. By the mid-1980
the only mechanical switches left in Alaska were owned by
the military, and they were gone by 1990.

Still, I don't think anyone *ever* used E type repeaters
in Alaska, but I could be wrong on that.

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.

The general design paradigm used now is to put
"remotes" at multiple strategic sites and control
them all from one digital switch. Of course all of
these are trunked together, and the whole idea is to
prevent long loops while also requiring administration
of only a single digital switch.

That was a basic design decision made for telco's by the
vendors, back in the late 80's or early 90's. It was
enforced with system pricing! Nortel (NTI at the time),
for example, simply made the software for a digital
switch (actually, the long term use and maintenance of
the software) far more expensive than installing
remotes. It became uneconomical to have two switches in
any jurisdiction where it was possible to deactivate one
and replace it and move forward with remotes.

By the mid-1990's all of NTI's customer base had moved
in that direction.

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.

My concern was only the State of Alaska... which is
of course the size of 20% of the entire Lower-48.

 

[Arny Krueger]

OK, Arny - what are the distinguishing characteristics of
an "analog line"?

The presence of a signal that is an electrical analog of the data being
transmitted.

IOW, it might be that if I send data that represents two or three times as
much value, it measures as having about two or three times the amplitude.

There are some interesting analog lines with complex interpretations, such
as those that are used to transmit rotational information - the 5 wires
between two selsyn motors for example.

Once we have determined that we have
an "analog line," does this mean that said line cannot possibly
be used to carry "digital" information?

Not at all. At the most fundamental level, all transmission lines transmit
analog signals, whether the data is digitally coded or not.

If not, then what is the significance of designating said line to be
"analog" in the
first place?

The absence of digital coding, for one thing. Back in the old days, all
lines were analog. I think that maybe the telegraph put an end to that.
Morse code is a sort of PWM, right? ;-)

 

[glen herrmannsfeldt]

Don Pearce wrote:

(snip)

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.

It doesn't matter, the probability of it being equal is zero.
(not counting delta functions).

-- glen

 

[Jerry Avins]

Floyd L. Davidson wrote:

...

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

I don't recall your being explicit about the origin or basis for that
definition.

US cash transactions are quantized to the nearest penny. Does that make
money digital?

Jerry

 

[Floyd L. Davidson]

Why? What does that mean, EXACTLY, that

I've given you the URL for a glossary of terms, why
don't you use it? Here are some others:

http://www.atis.org/tg2k/
http://www.itu.int/sancho/index.asp
http://www.carrieraccessbilling.com/telecommunications-glossary-a.asp
http://www.faxswitch.com/Definitions/

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?

Quasi-Analog Signal -

A digital signal that has been converted to a form
suitable for transmission over a specified analog
channel.

 

[Don Pearce]

Don Pearce wrote:

(snip)


It doesn't matter, the probability of it being equal is zero.
(not counting delta functions).

-- glen

Don't be a twat Glen, we are talking about definitions and whether
they are correct or not.

d

 

[Bob Myers]

The presence of a signal that is an electrical analog of the data being
transmitted.

OK, my apologies; I was under the impression that you
considered the line ITSELF to be "analog."

Not at all. At the most fundamental level, all transmission lines transmit
analog signals, whether the data is digitally coded or not.

Well, I would agree that they carry *electrical* signals; they
are not necessarily either "analog" or "digital" unless
someone (whoever THAT might be) insists on using "analog"
to mean "continuous," when there's already a perfectly good
word at hand (for instance, uh...."continuous!") that can be
used for that.

Bob M.

 

[Bob Myers]

I've given you the URL for a glossary of terms, why
don't you use it? Here are some others:

You keep thinking people are asking for definitions,
when in fact they are asking what terms mean
TO YOU. In other words, do you have any real
*understanding* of the meanings or implications of
what you're saying, or are you merely here to parrot
the words of others without actually bothering to
understand them?

Bob M.

 

[glen herrmannsfeldt]

Arny Krueger wrote:

(snip)

Sure I can. If I look at a line between two V-90 modems, I can immediately
see that it is an analog line. It may be carrying audio or video, but thats
about the data that is being carried, not the signal that I'm looking at.

I don't believe V.90 works that way. That is, you can't connect two
V.90 modems together that way.

The answer end of a V.90 connection must be an ISDN line, usually a
primary rate line with 24 channels. The result is that there is only
one A/D and D/A conversion between the two end points.

You may say that an ISDN line is an analog line since you can measure
the voltage on the wire as a function of time. I won't try to argue
either way on that one.

-- glen

 

[Jim Kelley]

The circuit which performs the quantisation *is* an analogue to digital
converter.

There's a difference between quantization and quantification. A sample
and hold, for example, quantizes an analog signal. It is considered
quantized because a signal might now be represented as a series of
sampled levels rather than a continuously varying level. But the held
samples are not digitized until they have been quantified, i.e. a
number has been assigned to each sample that is ratiometric with the
analog quantity being digitized. In the digital domain, the signal is
comprised of a series of numbers each of which represents a discrete
(quantized) analog value.

An important property of practical digital components is that they
regenerate the signal. If you define e.g. the range 0V-2V as "zero" and
3V-5V as "one", then each component will accept outputs which are near the
edges of the range and produce outputs which are further from the edges
(i.e. less ambiguous).

That is a property of binary logic circuits. The two states may
literally be representative of on and off rather than one and zero.
There may be nothing at all 'digital' about such circuits.

jk

 

[Floyd L. Davidson]

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."

That is not true. See the definition of analog data and
digital data.

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.

Wrong.

Shannon discussed the theory of digital channels with
and without noise. He defined it as "a discrete channel
will mean a system whereby a sequence of choices from a
finite set ... can be transmitted ..."

He then discussed the theory of analog channels, which
began with, "We now consider the case where the
signals or the messages or both are continuously
variable, in contrast with the discrete nature assumed
heretofore."

Clearly his definitions were consistent with those that
have been cited. Of course that again is just another
horrible appeal to authority... ;-)

As it infinite number of values, one of his initial examples
is an ensemble that represents white noise... which is
a summation all values from negative infinity to positive
infinity. Heh heh, not just an infinite number of values,
but 2 times infinity...

Seems like they would've called it "quantized," then,

It doesn have to be quanitized. But if something is
quantized it certainly then is a set of discete values.

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?

You just did confuse them. I just set the record straight,
again. How many times will it take for you to understand
what quantize means? Do you need the definition posted
again?

 

[Bob Myers]

The telegraph and digital communication came first.

http://en.wikipedia.org/wiki/Telegraph

And before that, the hollow log with sticks, or smoke
signals....;-)

(Which for some reason reminds me of the old Far Side
cartoon with the two South-Sea-Island-type natives
watching bubbles coming out of the nearby volcano, with
one saying to the other, "Well, whatever the gods are, they're
not angry!" )

Bob M.

 

[Floyd L. Davidson]

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

You cannot have have not.

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.

What evidence and what reason? You have no evidence,
and your reasoning is not authoritative.

I deleted all of your wallowing and weaseling.

The standard definitions stand.

 

[Floyd L. Davidson]

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

That's why he has postes sooooo many!