Digital, or analog?

[Jerry Avins]

It seems to me important to agree on criteria for deciding whether a
particular circuit or signal is digital or analog

One criterion is intended use; there seems to be general agreement about
that, so I don't address it here. Another criterion is the nature if the
signal or circuit itself, without reference to intentions. That is the
topic of this short essay.

*SIGNALS*
A digital signal consists of a sequence of a fixed number of discrete
states, with no intermediate states are allowed. Outside the realm of
quantum mechanics, a continuous signal is not digital. It can be made
digital by quantizing it, and different quantizers will convert the same
analog signal into different quantized signals. As far as I know,
digital signals exist only as abstractions and in computer circuits. I
would be delighted to learn of exceptions.

*CIRCUITS*
A circuit intended for a digital application has a fixed number of
discrete input and output states. The useful states are limited to those
common to both input and output. For simplicity of design, the number of
states is usually chosen to be 2, although other arrangements are
possible and some have been utilized. States are represented at outputs
as voltage or current ranges, and recognized at inputs in the same way.
The thresholds need not be the same at input or output. For example, the
specification for the 74LS logic family requires a high-level (1) to
equal or exceed 2 volts and a low level (0) to be no more than .8 volts
at the input, and guarantees that a 1 will be at least 2.4 volts and a 0
no more than .5 volts at the output. That specification makes the
devices well suited for digital use, but it defines them as analog
devices by defining voltages which are, as far as states go, ambiguous.

A CMOS CD4011B makes that point better. It is a quad 2-input NAND gate.
With a 15-volt supply, a 1 is 11 volts or greater, and a 0 is 4 volts or
less. The output swings between .05 and 14.95 volts when lightly loaded,
and can sink or source more than 5 ma at 4 and 11 volts. The /intended/
use of a NAND gate makes it digital devices, but these are inherently
analog by construction. Their inherent analog nature seen by connecting
a 1 megohm resistor from output to the inputs tied together. You will
have an analog amplifier with 23dB voltage gain and much higher power
gain. With capacitive coupling, the four gates can be connected as two H
bridges that will deliver 18 milliwatts per channel into 1500 ohms. To
be truly digital, a device must have discrete states, and be incapable
of exhibiting any other state.

That situation is approximated by cross coupling a pair of the gates to
make a set-reset flip-flop. Now there are only two stable states, but
the in-between states still exist as transient states passed through
when the device is in transition. Rise and fall times greater than zero,
and the well known but often ignored metastable state attest to that.
http://www.interfacebus.com/Design_MetaStable.html As far as I know,
digital circuits exist only as abstractions and on schematics. I would
be delighted to learn of exceptions.

Jerry
--
"The rights of the best of men are secured only as the
rights of the vilest and most abhorrent are protected."
- Chief Justice Charles Evans Hughes, 1927
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Eric Jacobsen]

On Wed, 01 Nov 2006 15:40:51 -0500, Jerry Avins <[email protected]> wrote:

>It seems to me important to agree on criteria for deciding whether a
>particular circuit or signal is digital or analog
>
>One criterion is intended use; there seems to be general agreement about
>that, so I don't address it here. Another criterion is the nature if the
>signal or circuit itself, without reference to intentions. That is the
>topic of this short essay.
>
>*SIGNALS*
>A digital signal consists of a sequence of a fixed number of discrete
>states, with no intermediate states are allowed. Outside the realm of
>quantum mechanics, a continuous signal is not digital. It can be made
>digital by quantizing it, and different quantizers will convert the same
>analog signal into different quantized signals. As far as I know,
>digital signals exist only as abstractions and in computer circuits. I
>would be delighted to learn of exceptions.
>
>*CIRCUITS*
>A circuit intended for a digital application has a fixed number of
>discrete input and output states. The useful states are limited to those
>common to both input and output. For simplicity of design, the number of
>states is usually chosen to be 2, although other arrangements are
>possible and some have been utilized. States are represented at outputs
>as voltage or current ranges, and recognized at inputs in the same way.
>The thresholds need not be the same at input or output. For example, the
>specification for the 74LS logic family requires a high-level (1) to
>equal or exceed 2 volts and a low level (0) to be no more than .8 volts
>at the input, and guarantees that a 1 will be at least 2.4 volts and a 0
>no more than .5 volts at the output. That specification makes the
>devices well suited for digital use, but it defines them as analog
>devices by defining voltages which are, as far as states go, ambiguous.
>
>A CMOS CD4011B makes that point better. It is a quad 2-input NAND gate.
>With a 15-volt supply, a 1 is 11 volts or greater, and a 0 is 4 volts or
>less. The output swings between .05 and 14.95 volts when lightly loaded,
>and can sink or source more than 5 ma at 4 and 11 volts. The /intended/
>use of a NAND gate makes it digital devices, but these are inherently
>analog by construction. Their inherent analog nature seen by connecting
>a 1 megohm resistor from output to the inputs tied together. You will
>have an analog amplifier with 23dB voltage gain and much higher power
>gain. With capacitive coupling, the four gates can be connected as two H
>bridges that will deliver 18 milliwatts per channel into 1500 ohms. To
>be truly digital, a device must have discrete states, and be incapable
>of exhibiting any other state.
>
>That situation is approximated by cross coupling a pair of the gates to
>make a set-reset flip-flop. Now there are only two stable states, but
>the in-between states still exist as transient states passed through
>when the device is in transition. Rise and fall times greater than zero,
>and the well known but often ignored metastable state attest to that.
>http://www.interfacebus.com/Design_MetaStable.html As far as I know,
>digital circuits exist only as abstractions and on schematics. I would
>be delighted to learn of exceptions.
>
>Jerry

Jerry, that's good work on a rational foundation for the terms.

I think, however, that the significant quibbling comes in only on
boundary cases where the distinction gets blurred, and it's just
always going to be tough to avoid semantic arguments popping up there.
For example, even with "digital" devices, by your definitions, at both
ends of a circuit board trace, the trace may still need carefully
designed termination and interference isolation which are often best
treated as "analog" phenomena.

Although your definitions generally hold, there's still plenty of room
for argument and confusion at the boundaries. Because of that, I
don't think the problem of whether certain things are really "digital"
or "analog" is going to be solved with world-class
unanimously-approved definitions.

Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org

[Ron N.]

Jerry Avins wrote:
> It seems to me important to agree on criteria for deciding whether a
> particular circuit or signal is digital or analog
....
> As far as I know, digital circuits exist only as abstractions ...

I remember an old-time engineer once telling me "There
is no such thing as digital". We merely interpret certain
behaviors of analog circuits as transitions, noise, or
metastability, etc. and then attempt to ignore those for
our convenience, or at our own peril.

Of course, he was talking about the real world. We are
free to make abstract models, but should not confuse
a model with some engineering reality, especially if
a circuit is working near its limits of behaving similar
to our first-order models.

So I would agree with you that digital circuits exist only
as abstractions.

However, there is also no such thing as analog. It is
merely a model where we assume that some continuous
curve or function is associated with our measurements
of what are actually numbers discrete quantum events
(the measurements are usually far too course to
notice the error).

If the quantum events are below some noise floor and
you are already ignoring this noise floor, then a continuous
model might be the computationally or cognitively more
efficient tool of abstraction.

So, as to the question about whether some circuit or
signal is digital or analog, I would say the answer
depends on which model best serves your specific
purpose or question regarding the given circuit or signal.

For some things DSP engineers do, the answer might
well be both.


IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M

[Richard Owlett]

Jerry Avins wrote:
> [snip much]
> As far as I know,
> digital circuits exist only as abstractions and on schematics. I would
> be delighted to learn of exceptions.
>

electo-mechanical relays

'nuff said ;)

[Adrian Spilca]

Jerry Avins wrote:

> It seems to me important to agree on criteria for deciding whether a
> particular circuit or signal is digital or analog
>
> One criterion is intended use; there seems to be general agreement about
> that, so I don't address it here. Another criterion is the nature if the
> signal or circuit itself, without reference to intentions. That is the
> topic of this short essay.
>
> *SIGNALS*
> A digital signal consists of a sequence of a fixed number of discrete
> states, with no intermediate states are allowed. Outside the realm of
> quantum mechanics, a continuous signal is not digital. It can be made
> digital by quantizing it, and different quantizers will convert the same
> analog signal into different quantized signals. As far as I know,
> digital signals exist only as abstractions and in computer circuits. I
> would be delighted to learn of exceptions.
>
> *CIRCUITS*
> A circuit intended for a digital application has a fixed number of
> discrete input and output states. The useful states are limited to those
> common to both input and output. For simplicity of design, the number of
> states is usually chosen to be 2, although other arrangements are
> possible and some have been utilized. States are represented at outputs
> as voltage or current ranges, and recognized at inputs in the same way.
> The thresholds need not be the same at input or output. For example, the
> specification for the 74LS logic family requires a high-level (1) to
> equal or exceed 2 volts and a low level (0) to be no more than .8 volts
> at the input, and guarantees that a 1 will be at least 2.4 volts and a 0
> no more than .5 volts at the output. That specification makes the
> devices well suited for digital use, but it defines them as analog
> devices by defining voltages which are, as far as states go, ambiguous.
>
> A CMOS CD4011B makes that point better. It is a quad 2-input NAND gate.
> With a 15-volt supply, a 1 is 11 volts or greater, and a 0 is 4 volts or
> less. The output swings between .05 and 14.95 volts when lightly loaded,
> and can sink or source more than 5 ma at 4 and 11 volts. The /intended/
> use of a NAND gate makes it digital devices, but these are inherently
> analog by construction. Their inherent analog nature seen by connecting
> a 1 megohm resistor from output to the inputs tied together. You will
> have an analog amplifier with 23dB voltage gain and much higher power
> gain. With capacitive coupling, the four gates can be connected as two H
> bridges that will deliver 18 milliwatts per channel into 1500 ohms. To
> be truly digital, a device must have discrete states, and be incapable
> of exhibiting any other state.
>
> That situation is approximated by cross coupling a pair of the gates to
> make a set-reset flip-flop. Now there are only two stable states, but
> the in-between states still exist as transient states passed through
> when the device is in transition. Rise and fall times greater than zero,
> and the well known but often ignored metastable state attest to that.
> http://www.interfacebus.com/Design_MetaStable.html As far as I know,
> digital circuits exist only as abstractions and on schematics. I would
> be delighted to learn of exceptions.
>
> Jerry

Yes, our world is analog, isn't it?
I agree that the digital world is an abstraction, therefore not real.

But what is our world or what is real? (keeping the technological
perspective rather than philosophical). Isn't it because our sensors
integrate incoming signals so that they appear continuous? (I prefer
continuous rather than analog, as opposed to digital). Because our world,
the real world, is what we perceive using our natural sensors. But this is
the macroscopic world, in the microscopic one (as you mentioned quantum
mechanics) it could be the other way around. The continuous signals might
be the abstraction.

Adrian

[Jerry Avins]

Richard Owlett wrote:
> Jerry Avins wrote:
>> [snip much]
> > As far as I know,
>> digital circuits exist only as abstractions and on schematics. I would
>> be delighted to learn of exceptions.
>>
>
> electo-mechanical relays
>
> 'nuff said ;)

Better say more. Make before break, or break before make? We're looking
at transitions here. Even with SPST, contacts bounce

Jerry
--
"The rights of the best of men are secured only as the
rights of the vilest and most abhorrent are protected."
- Chief Justice Charles Evans Hughes, 1927
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Ron N.]

Richard Owlett wrote:
> Jerry Avins wrote:
> > [snip much]
> > As far as I know,
> > digital circuits exist only as abstractions and on schematics. I would
> > be delighted to learn of exceptions.
> >
>
> electo-mechanical relays
>
> 'nuff said ;)

The first time I tried to make a toggle flip flop out of
relays (in junior high, I think), it went into metastable
oscillation, dependent on the power supply voltage.

Another DPDT relay (there were scavenged discards)
had one bad (randomly high resistance) contact.

Try again. :-)


IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M

[Richard Owlett]

Jerry Avins wrote:

> Richard Owlett wrote:
>
>> Jerry Avins wrote:
>>
>>> [snip much]
>>
>> > As far as I know,
>>
>>> digital circuits exist only as abstractions and on schematics. I
>>> would be delighted to learn of exceptions.
>>>
>>
>> electo-mechanical relays
>>
>> 'nuff said ;)
>
>
> Better say more. Make before break, or break before make? We're looking
> at transitions here. Even with SPST, contacts bounce
>
> Jerry


The contacts have *ONLY* 2 states.

No matter how much bounce, the contacts are *EITHER* "open" or "closed"

ain't no other option!


Now as to a "system", can you make it emulate 'analog'? YEPP.

Does that make relay analog? NOPE.

Disagree? well, zip is now 658xx so "SHOW ME" ;)

[Ron N.]

Richard Owlett wrote:
> The contacts have *ONLY* 2 states.
>
> No matter how much bounce, the contacts are *EITHER* "open" or "closed"

Said by somebody who's never put a VOM across a batch
of old rusted relays (scavenged from dead pinball machine
parts found in a outdoor scrap heap I think).

Your abstraction does work a bit better with new ones.


IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M

[Jerry Avins]

Richard Owlett wrote:
> Jerry Avins wrote:
>
>> Richard Owlett wrote:
>>
>>> Jerry Avins wrote:
>>>
>>>> [snip much]
>>>
>>> > As far as I know,
>>>
>>>> digital circuits exist only as abstractions and on schematics. I
>>>> would be delighted to learn of exceptions.
>>>>
>>>
>>> electo-mechanical relays
>>>
>>> 'nuff said ;)
>>
>>
>> Better say more. Make before break, or break before make? We're
>> looking at transitions here. Even with SPST, contacts bounce
>>
>> Jerry
>
>
> The contacts have *ONLY* 2 states.
>
> No matter how much bounce, the contacts are *EITHER* "open" or "closed"
>
> ain't no other option!

Arcing contacts? Zero risetime?

Jerry
--
"The rights of the best of men are secured only as the
rights of the vilest and most abhorrent are protected."
- Chief Justice Charles Evans Hughes, 1927
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Richard Owlett]

Ron N. wrote:

> Richard Owlett wrote:
>
>>The contacts have *ONLY* 2 states.
>>
>>No matter how much bounce, the contacts are *EITHER* "open" or "closed"
>
>
> Said by somebody who's never put a VOM across a batch
> of old rusted relays (scavenged from dead pinball machine
> parts found in a outdoor scrap heap I think).
>
> Your abstraction does work a bit better with new ones.
>
>
> IMHO. YMMV.

BULL!
irregardless of "contact resistance" they are *either* open/closed

[Richard Owlett]

Jerry Avins wrote:

> Richard Owlett wrote:
>
>> Jerry Avins wrote:
>>
>>> Richard Owlett wrote:
>>>
>>>> Jerry Avins wrote:
>>>>
>>>>> [snip much]
>>>>
>>>>
>>>> > As far as I know,
>>>>
>>>>> digital circuits exist only as abstractions and on schematics. I
>>>>> would be delighted to learn of exceptions.
>>>>>
>>>>
>>>> electo-mechanical relays
>>>>
>>>> 'nuff said ;)
>>>
>>>
>>>
>>> Better say more. Make before break, or break before make? We're
>>> looking at transitions here. Even with SPST, contacts bounce
>>>
>>> Jerry
>>
>>
>>
>> The contacts have *ONLY* 2 states.
>>
>> No matter how much bounce, the contacts are *EITHER* "open" or "closed"
>>
>> ain't no other option!
>
>
> Arcing contacts? Zero risetime?
>
> Jerry

BAHH see reply to Ron

[Ron N.]

Richard Owlett wrote:
> > Richard Owlett wrote:
> >
> >>The contacts have *ONLY* 2 states.
> >>
> >>No matter how much bounce, the contacts are *EITHER* "open" or "closed"

> irregardless of "contact resistance" they are *either* open/closed

So what resistance value, and for what duration, would you
call closed?

Do you think that all "open" relays have zero resistance?


IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M

[Floyd L. Davidson]

Richard Owlett <[email protected]> wrote:
>Jerry Avins wrote:
>> [snip much]
> > As far as I know,
>> digital circuits exist only as abstractions and on
>> schematics. I would be delighted to learn of exceptions.
>>
>
>electo-mechanical relays
>
>'nuff said ;)

I don't think it is possible to say enough to convince some
folks.

I'd say a light switch is another excellent example of something
clearly digital. That can be compared with a large variable
resistor (a "light dimmer") which is analog.

With a switch, the light is either on or off. With the dimmer,
the light can be set half way between any two other points.

One is discrete, the other is continuous. Digital, and analog.


--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) [email protected]

[Richard Owlett]

Ron N. wrote:
> Richard Owlett wrote:
>
>>>Richard Owlett wrote:
>>>
>>>
>>>>The contacts have *ONLY* 2 states.
>>>>
>>>>No matter how much bounce, the contacts are *EITHER* "open" or "closed"
>
>
>>irregardless of "contact resistance" they are *either* open/closed
>
>
> So what resistance value, and for what duration, would you
> call closed?

"closed" is CLOSED "open" is OPEN

>
> Do you think that all "open" relays have zero resistance?

NO *OPEN* relays have INFINITE resistance
actually i'm not cheating fair as i knew what you meant

My previous experience was in industry that wished to "KNOW" within 1 ms
when a contact closed with 10's to 100's of ms bounce
>
>
> IMHO. YMMV.

[Ron N.]

Richard Owlett wrote:
> Ron N. wrote:
> > Richard Owlett wrote:
> >
> >>>Richard Owlett wrote:
> >>>
> >>>
> >>>>The contacts have *ONLY* 2 states.
> >>>>
> >>>>No matter how much bounce, the contacts are *EITHER* "open" or "closed"
> >
> >
> >>irregardless of "contact resistance" they are *either* open/closed
> >
> >
> > So what resistance value, and for what duration, would you
> > call closed?
>
> "closed" is CLOSED "open" is OPEN
>
> >
> > Do you think that all "open" relays have zero resistance?
>
> NO *OPEN* relays have INFINITE resistance

That's what I get for looking at the wrong pin of a DPDT
relay. :^)

> actually i'm not cheating fair as i knew what you meant
>
> My previous experience was in industry that wished to "KNOW" within 1 ms
> when a contact closed with 10's to 100's of ms bounce

In my case, it was what voltage, frequency and duration
of an oscillating relay pair would close the next (rusty)
relay downstream. There was also the amplitude of
whacking the side of the breadboard. Analog.


> > IMHO. YMMV.

[Jerry Avins]

Richard Owlett wrote:
> Ron N. wrote:
>
>> Richard Owlett wrote:
>>
>>> The contacts have *ONLY* 2 states.
>>>
>>> No matter how much bounce, the contacts are *EITHER* "open" or "closed"
>>
>>
>> Said by somebody who's never put a VOM across a batch
>> of old rusted relays (scavenged from dead pinball machine
>> parts found in a outdoor scrap heap I think).
>>
>> Your abstraction does work a bit better with new ones.
>>
>>
>> IMHO. YMMV.
>
> BULL!
> irregardless of "contact resistance" they are *either* open/closed

You could say the same about a door, but degree matters, especially to
the obese.

Jerry
--
"The rights of the best of men are secured only as the
rights of the vilest and most abhorrent are protected."
- Chief Justice Charles Evans Hughes, 1927
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Richard Owlett]

Jerry Avins wrote:

> Richard Owlett wrote:
>
>> Ron N. wrote:
>>
>>> Richard Owlett wrote:
>>>
>>>> The contacts have *ONLY* 2 states.
>>>>
>>>> No matter how much bounce, the contacts are *EITHER* "open" or "closed"
>>>
>>>
>>>
>>> Said by somebody who's never put a VOM across a batch
>>> of old rusted relays (scavenged from dead pinball machine
>>> parts found in a outdoor scrap heap I think).
>>>
>>> Your abstraction does work a bit better with new ones.
>>>
>>>
>>> IMHO. YMMV.
>>
>>
>> BULL!
>> irregardless of "contact resistance" they are *either* open/closed
>
>
> You could say the same about a door, but degree matters, especially to
> the obese.
>
> Jerry

CAREFUL I out weigh you at least 3 to 2, even if decade younger ;)

[Ron N.]

Jerry Avins wrote:
> Richard Owlett wrote:

> > The contacts have *ONLY* 2 states.
> >
> > No matter how much bounce, the contacts are *EITHER* "open" or "closed"
> >
> > ain't no other option!
>
> Arcing contacts? Zero risetime?

I can't remember where, but I seem to recall some
ultra high-speed photography of the formation of an
arc. It didn't look like it was happening instantly.

Or does Richard count that first electron at "closed"?


IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M

[Bob Myers]

"Jerry Avins" <[email protected]> wrote in message
news:[email protected]...
> It seems to me important to agree on criteria for deciding whether a
> particular circuit or signal is digital or analog

Circuits and signals themselves are neither digital nor
analog, even though we unfortunately do tend to classify
them as such.

The terms "digital" and "analog" properly refer only to two
different means of encoding information, in this context
on to an electrical signal. The signal itself remains just
electricity no matter what we call the encoding, and all
signals and circuits obey the same basic physical laws, etc..
The true distinction between these two arises SOLELY in
how we interpret the signal (or similarly, how it was
intended to be interpreted).

In an "analog" encoding, some parameter of the electrical
signal (generally, either voltage or current, but there are
other possibilities) is manipulated such that it varies in a
manner directly related to the variations seen in the original
information source - for instance, a voltage which is caused
to vary in the same manner as a sound wave, in the case of
an "analog audio signal." And hence the name itself - the
voltage is varying ANALOGOUSLY to the original, hence
"analog" encoding.

Similarly, in a "digital" information encoding or transmission
system, various states of the transmitted signal correspond
to numeric values - or more generally, symbols - and must
be interpreted accordingly. Again, the name says it all -
we're not sending something that directly represents another
thing, but instead are sending symbols or "digits."

Neither term NECESSARILY implies a lot of what are
commonly thought of as the distinguishing features of
either; for instance, "analog" does not necessarily imply
that the system is either continuous or linear, even though
many common analog systems are both. Similarly, "digital"
does not necessarily imply a discrete or sampled representation,
and certainly is not limited to a straight binary encoding -
although again the vast majority of "digital" systems exhibit
these characteristics.

From this perspective, arguments as to whether the world
itself, or basic natural phenomena, etc., are "digital" or
"analog" are meaningless; the world is what the world is,
and these terms only refer to methods for encoding
information which describe some real, original thing.

We still refer to circuits themselves as "digital" or "analog"
primarily because of the optimization of that class of circuits
for dealing with that sort of information, but again the ciruits
themselves ALL behave according to the same laws of
physics. And there are certainly types of circuits which
don't fall into either category - power systems being the
most obvious example. (The transmission of power does
not involve the transmission of information, so to speak of
power engineering as dealing with either "analog" or
"digital" is just silly.)

Bob M.

[Floyd L. Davidson]

Jerry Avins <[email protected]> wrote:
>Richard Owlett wrote:
>> Ron N. wrote:
>>
>>> Richard Owlett wrote:
>>>
>>>> The contacts have *ONLY* 2 states.
>>>>
>>>> No matter how much bounce, the contacts are *EITHER* "open" or "closed"
>>>
>>>
>>> Said by somebody who's never put a VOM across a batch
>>> of old rusted relays (scavenged from dead pinball machine
>>> parts found in a outdoor scrap heap I think).
>>>
>>> Your abstraction does work a bit better with new ones.
>>>
>>>
>>> IMHO. YMMV.
>> BULL!
>> irregardless of "contact resistance" they are *either* open/closed
>
>You could say the same about a door, but degree matters,
>especially to the obese.

Then obesity is clearly analog. But the described switch contacts
are not...

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) [email protected]

[Floyd L. Davidson]

"Bob Myers" <[email protected]> wrote:
>Neither term NECESSARILY implies a lot of what are
>commonly thought of as the distinguishing features of
>either; for instance, "analog" does not necessarily imply
>that the system is either continuous or linear, even though
>many common analog systems are both.

By definition, it implys that it is continous. Linear, no, but
continuous is essential.

>Similarly, "digital"
>does not necessarily imply a discrete

Discrete, yes, again by definition.

> or sampled representation,
>and certainly is not limited to a straight binary encoding -
>although again the vast majority of "digital" systems exhibit
>these characteristics.

I don't believe that necessarily most are binary nor sampled.

>From this perspective, arguments as to whether the world

From this perspective, if you want to make up your own
definitions, and so does everyone else, what point is there to
discussing *anything*?

You are denying that the standardized definitions are correct,
and that is an absurd stance to take, which makes *nothing* you
say worth discussing.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) [email protected]

[Ron N.]

Floyd L. Davidson wrote:
> You are denying that the standardized definitions are correct,
> and that is an absurd stance to take,

I disagree. Many standardized definitions are committee
compromises, and have sometimes what comes out of a
committee has little to do with what real people try to mean
or understand when using those words (especially if a
committee has gotten politicized or influenced by marketing
agendas).

(in general. not expressing an opinion on digital/analog).
IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M

[Richard Owlett]

Ron N. wrote:

> Jerry Avins wrote:
>
>>Richard Owlett wrote:
>
>
>>>The contacts have *ONLY* 2 states.
>>>
>>>No matter how much bounce, the contacts are *EITHER* "open" or "closed"
>>>
>>>ain't no other option!
>>
>>Arcing contacts? Zero risetime?
>
>
> I can't remember where, but I seem to recall some
> ultra high-speed photography of the formation of an
> arc. It didn't look like it was happening instantly.
>
> Or does Richard count that first electron at "closed"?
>
>

OK let's not tooooo far to the extreme .

So a relay is "analogue" in sense that on closure its resistance may
change "gradually" from 10^10 ohms thru 10^8 ohms to 10^-3 ohms.

And I've worked with "analog" systems capable of noticing individual
electrons as they came. Had an interesting argument with bull-headed
chemistry post doc that some of his instrumentation requirements were
silly as they implied capability of measuring tenths of electrons per
second -- can anyone say "gain bandwidth product". I "lost" as I was
ONLY a technician he was a *PHD*

[Richard Owlett]

Bob Myers wrote:

> "Jerry Avins" <[email protected]> wrote in message
> news:[email protected]...
>
>>It seems to me important to agree on criteria for deciding whether a
>>particular circuit or signal is digital or analog
>
>
> Circuits and signals themselves are neither digital nor
> analog, even though we unfortunately do tend to classify
> them as such.
>

I've seen a 7400 series inverter used as an 'op amp'
Don't recall why it was done, suspect was just to prove it could be ;/

[Floyd L. Davidson]

"Ron N." <[email protected]> wrote:
>Floyd L. Davidson wrote:
>> You are denying that the standardized definitions are correct,
>> and that is an absurd stance to take,
>
>I disagree. Many standardized definitions are committee
>compromises,

I was not referencing just *any* definitions. I say *those*
definitions. They are not in dispute by any reputable source.

You stake *your* reputation against the entire industry when
you deny they are correct, and that is simply absurd!

>and have sometimes what comes out of a
>committee has little to do with what real people try to mean
>or understand when using those words (especially if a
>committee has gotten politicized or influenced by marketing
>agendas).
>
>(in general. not expressing an opinion on digital/analog).
>IMHO. YMMV.

So we are going to ignore indisputably good standardized
definitions that the industry (not to mention the Federal
government) uses, and you think that is going to in any way
assist in discussing this topic???

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) [email protected]

[Floyd L. Davidson]

Richard Owlett <[email protected]> wrote:
>Bob Myers wrote:
>> Circuits and signals themselves are neither digital nor
>> analog, even though we unfortunately do tend to classify
>> them as such.
>
>I've seen a 7400 series inverter used as an 'op amp'
>Don't recall why it was done, suspect was just to prove it could be ;/

Of course to make it work as an analog circuit... components had
to be added. Which means that was *not* the same "circuit"
which functions as a digital circuit, even if it used the same
IC.

Circuits may or may not be analog or digital, though *clearly*
some are one or the other. Signals *are* one or the other, by
definition.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) [email protected]

[John E. Hadstate]

"Bob Myers" <[email protected]> wrote in message
news:[email protected]...
>
> "Jerry Avins" <[email protected]> wrote in message
> news:[email protected]...

>> It seems to me important to agree on criteria for
>> deciding whether a particular circuit or signal is
>> digital or analog

This is a general prerequisite for any kind of
communication, digital or analog ;-)

>
> Circuits and signals themselves are neither digital nor
> analog, even though we unfortunately do tend to classify
> them as such.
>

That is demonstrably incorrect. All circuits that have a
physical instantiation are analog, as are the signals that
they process.

[snip fairly lucid description of analog encoding]

> Similarly, in a "digital" information encoding or
> transmission
> system, various states of the transmitted signal
> correspond
> to numeric values - or more generally, symbols - and must
> be interpreted accordingly. Again, the name says it all -
> we're not sending something that directly represents
> another
> thing, but instead are sending symbols or "digits."

In and of itself, a digital state has no representation in
the physical world. To instantiate or process a digital
state, it must be encoded into a voltage/current analog.
People have been known to group binary states into a
multi-state logic and represent the combined states with a
single value of voltage/current analog. If you group enough
binary states together the analog of the digital value
becomes indistinguishable from continuous.

[Richard Owlett]

Floyd L. Davidson wrote:

> Richard Owlett <[email protected]> wrote:
>
>>Bob Myers wrote:
>>
>>>Circuits and signals themselves are neither digital nor
>>>analog, even though we unfortunately do tend to classify
>>>them as such.
>>
>>I've seen a 7400 series inverter used as an 'op amp'
>>Don't recall why it was done, suspect was just to prove it could be ;/
>
>
> Of course to make it work as an analog circuit... components had
> to be added. Which means that was *not* the same "circuit"
> which functions as a digital circuit, even if it used the same
> IC.
>
> Circuits may or may not be analog or digital, though *clearly*
> some are one or the other. Signals *are* one or the other, by
> definition.
>

COMPONENTS ;? :?
2 resistors ;/
Basically we agree :>

[Floyd L. Davidson]

Richard Owlett <[email protected]> wrote:
>Floyd L. Davidson wrote:
>
>> Richard Owlett <[email protected]> wrote:
>>
>>>Bob Myers wrote:
>>>
>>>>Circuits and signals themselves are neither digital nor
>>>>analog, even though we unfortunately do tend to classify
>>>>them as such.
>>>
>>>I've seen a 7400 series inverter used as an 'op amp'
>>>Don't recall why it was done, suspect was just to prove it could be ;/
>>
>> Of course to make it work as an analog circuit... components
>> had
>> to be added. Which means that was *not* the same "circuit"
>> which functions as a digital circuit, even if it used the same
>> IC.
>> Circuits may or may not be analog or digital, though *clearly*
>> some are one or the other. Signals *are* one or the other, by
>> definition.
>>
>
>COMPONENTS ;? :?
>2 resistors ;/
>Basically we agree :>

Yes, exactly! The two resistors are only a slight addition, but
of course they dramatically change the way the circuit works!

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) [email protected]

[Eric Jacobsen]

On Thu, 02 Nov 2006 01:39:32 -0900, [email protected] (Floyd L.
Davidson) wrote:

>"Ron N." <[email protected]> wrote:
>>Floyd L. Davidson wrote:
>>> You are denying that the standardized definitions are correct,
>>> and that is an absurd stance to take,
>>
>>I disagree. Many standardized definitions are committee
>>compromises,
>
>I was not referencing just *any* definitions. I say *those*
>definitions. They are not in dispute by any reputable source.
>
>You stake *your* reputation against the entire industry when
>you deny they are correct, and that is simply absurd!
>
>>and have sometimes what comes out of a
>>committee has little to do with what real people try to mean
>>or understand when using those words (especially if a
>>committee has gotten politicized or influenced by marketing
>>agendas).
>>
>>(in general. not expressing an opinion on digital/analog).
>>IMHO. YMMV.
>
>So we are going to ignore indisputably good standardized
>definitions that the industry (not to mention the Federal
>government) uses, and you think that is going to in any way
>assist in discussing this topic???

Ron and I have both worked in standards bodies helping to write
standards, so we have a little different perspective on this.

A standard is typically intended only to reduce confusion in the
context for which it is intended.

e.g., the form factor for electrical wall outlets and plugs are
"standardized" around the world, but they're different standards. You
can go to Europe (or any of a host of places) around the world and
argue until you're blue in the face that "the standard" electrical
plug looks like the US version, and you can produce the drawings and
definitions to prove it, but you'll still not be able to plug in into
an outlet in the UK or Germany or Japan or China or Russia or a host
of other places. You'll be right in the context of the US, but it
won't help you run your shaver over there.

You insist on using a single definition that you pulled out of a
"standard" somewhere. It's causing you trouble and you don't seem to
be able to recognize that outside of the context for which that
standard was developed it's no longer "the" definition, just "a"
definition. Anyone else's definition is as arguably good here as the
one's you've cited, hence the current discussion.



Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org

[Bob Myers]

"Floyd L. Davidson" <[email protected]> wrote in message
news:[email protected]...
> "Ron N." <[email protected]> wrote:
>>Floyd L. Davidson wrote:
>>> You are denying that the standardized definitions are correct,
>>> and that is an absurd stance to take,
>>
>>I disagree. Many standardized definitions are committee
>>compromises,
>
> I was not referencing just *any* definitions. I say *those*
> definitions. They are not in dispute by any reputable source.

Well, not as long as YOU get to pick which sources are
to be considered "reputable" and which aren't...

Bob M.

[Bob Myers]

"Floyd L. Davidson" <[email protected]> wrote in message
news:[email protected]...
> "Bob Myers" <[email protected]> wrote:
>>Neither term NECESSARILY implies a lot of what are
>>commonly thought of as the distinguishing features of
>>either; for instance, "analog" does not necessarily imply
>>that the system is either continuous or linear, even though
>>many common analog systems are both.
>
> By definition, it implys that it is continous. Linear, no, but
> continuous is essential.

Let's try another simple example, shall we?

Last year, the organizers of a charity drive came to their
local electronics-tinkerer type, and told him that they
wanted to put a big display up that would show how
well they were doing toward meeting their year's goal.

"No problem," he says. "I can rig up a big meter movement
to this here variable resistor, we'll put it on a billboard,
and I'll label various points on the meter as '10%,' '20%,'
and so on. Each day, you send someone to the billboard,
and they can turn this knob to set the pointer to wherever
it needs to be that day!"

"Perfect!" they replied, and the new charity-drive billboard
went up. Worked like a charm, too. Each day, the
designated knob-twister would adjust the position of the
pointer, and everyone was happy with the result. Until
THIS year's drive, when they found that the big potentiometer
that the tinkerer had originally used burned out, and no
replacement was available.

"Still no problem," he says. "I'll just replace it with
a string of twenty or thirty discrete resistors, and you
can then move the pointer by choosing where in that
string you attach this alligator clip. It'll work just like
before!" And sure enough, it did.

The question at this point should be clear. The position
of the pointer on this big charity-drive billboard is
being controlled by the current coming up to the
meter movement in both cases - and also, quite clearly,
when the thing was first put up that this current can be
considered to be an analog representation of how
close this group is to their goal. After the modification
was made, though, the thing still works in exactly the
same manner - the information is being delivered to the
billboard via a current whose amplitude is "analogous to"
that information. It just is no longer capable of being
*continuously* adjusted.

Are you arguing that we now have a "digital" signal
going over that wire? And are you going to actually
think about your answer, or are you going to defer all
thought to some "standard"?


Bob M.

[Bob Myers]

"John E. Hadstate" <[email protected]> wrote in message
news:[email protected].. .
> That is demonstrably incorrect. All circuits that have a physical
> instantiation are analog, as are the signals that they process.

Well, it all depends on which definition of "analog"
you're using I guess. From the following comment:

>
> [snip fairly lucid description of analog encoding]
>

....I would have assumed that we were in agreement
there. In which case "analog" and "digital" BOTH refer
to how information is encoded onto a signal, but not
really the signal itself. Elsewhere I have given an example
of a signal which cannot be unambiguously classified as
either "analog" or "digital" in the common (and sloppy)
use of those terms merely by looking at it. Given that
confusion, I am simply proposing that if you really want
to see what's going on, you think of circuits and signals
as simply being "electrical" - and leave the words "analog"
and "digital" for use only in pointing to encodings.

Admittedly, most of us in the industry are VERY used to
using these terms another way (and I do so myself in many
cases), and it takes a real effort to change that perspective.
But it is very often valuable to do so. Far too often, I have
seen various claims of advantages or disadvantages in a given
system presented as being the result of something "being
analog" or "being digital," when in fact these concerns had
nothing to do with what was being considered.

Bob M.

[Ron N.]

Richard Owlett wrote:
> Ron N. wrote:
>
> > Jerry Avins wrote:
> >
> >>Richard Owlett wrote:
> >
> >
> >>>The contacts have *ONLY* 2 states.
> >>>
> >>>No matter how much bounce, the contacts are *EITHER* "open" or "closed"
> >>>
> >>>ain't no other option!
> >>
> >>Arcing contacts? Zero risetime?
> >
> >
> > I can't remember where, but I seem to recall some
> > ultra high-speed photography of the formation of an
> > arc. It didn't look like it was happening instantly.
> >
> > Or does Richard count that first electron at "closed"?
> >
> >
>
> OK let's not tooooo far to the extreme .
>
> So a relay is "analogue" in sense that on closure its resistance may
> change "gradually" from 10^10 ohms thru 10^8 ohms to 10^-3 ohms.

Right. But my point was that the model has to be chosen
depending on the question. We can still model a relay as
digital because the elevators don't usually show any measurable
difference in behavior due to these analog realities. And we
can model a relay as analog if we are looking at, say, the
effects of humidity & back-EMF on the life of contact plating.


IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M

[Eric Jacobsen]

On Thu, 02 Nov 2006 10:38:54 -0700, Eric Jacobsen
<[email protected]> wrote:

>Ron and I have both worked in standards bodies helping to write
>standards, so we have a little different perspective on this.

Oop, sorry, Ron, if that's not true. I was mistaken over who's post
was included here.


Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org

[CWatters]

"Richard Owlett" <[email protected]> wrote in message
news:[email protected]...

> > Do you think that all "open" relays have zero resistance?
>
> NO *OPEN* relays have INFINITE resistance
> actually i'm not cheating fair as i knew what you meant

I guess. As long as you don't measure it while the contacts are arcing :-)

[CWatters]

"Jerry Avins" <[email protected]> wrote in message
news:[email protected]...
> It seems to me important to agree on criteria for deciding whether a
> particular circuit or signal is digital or analog

The faster the digital circuit goes the more analog it becomes.

[Jerry Avins]

Richard Owlett wrote:
> Jerry Avins wrote:
>
>> Richard Owlett wrote:
>>
>>> Ron N. wrote:
>>>
>>>> Richard Owlett wrote:
>>>>
>>>>> The contacts have *ONLY* 2 states.
>>>>>
>>>>> No matter how much bounce, the contacts are *EITHER* "open" or
>>>>> "closed"
>>>>
>>>>
>>>>
>>>> Said by somebody who's never put a VOM across a batch
>>>> of old rusted relays (scavenged from dead pinball machine
>>>> parts found in a outdoor scrap heap I think).
>>>>
>>>> Your abstraction does work a bit better with new ones.
>>>>
>>>>
>>>> IMHO. YMMV.
>>>
>>>
>>> BULL!
>>> irregardless of "contact resistance" they are *either* open/closed
>>
>>
>> You could say the same about a door, but degree matters, especially to
>> the obese.
>>
>> Jerry
>
> CAREFUL I out weigh you at least 3 to 2, even if decade younger ;)

If you try to sit on me, I can squeeze through places you can't follow.

Jerry
--
"The rights of the best of men are secured only as the
rights of the vilest and most abhorrent are protected."
- Chief Justice Charles Evans Hughes, 1927
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Jerry Avins]

Richard Owlett wrote:
> Bob Myers wrote:
>
>> "Jerry Avins" <[email protected]> wrote in message
>> news:[email protected]...
>>
>>> It seems to me important to agree on criteria for deciding whether a
>>> particular circuit or signal is digital or analog
>>
>>
>> Circuits and signals themselves are neither digital nor
>> analog, even though we unfortunately do tend to classify
>> them as such.
>>
>
> I've seen a 7400 series inverter used as an 'op amp'
> Don't recall why it was done, suspect was just to prove it could be ;/

Lousy choice. The symmetric CD40xx, on the other hand, was well enough
suited to be used in at least onecommercial product.

jerry
--
"The rights of the best of men are secured only as the
rights of the vilest and most abhorrent are protected."
- Chief Justice Charles Evans Hughes, 1927
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Jerry Avins]

Bob Myers wrote:

> ... In which case "analog" and "digital" BOTH refer
> to how information is encoded onto a signal, but not
> really the signal itself. Elsewhere I have given an example
> of a signal which cannot be unambiguously classified as
> either "analog" or "digital" in the common (and sloppy)
> use of those terms merely by looking at it. Given that
> confusion, I am simply proposing that if you really want
> to see what's going on, you think of circuits and signals
> as simply being "electrical" - and leave the words "analog"
> and "digital" for use only in pointing to encodings.
>
> Admittedly, most of us in the industry are VERY used to
> using these terms another way (and I do so myself in many
> cases), and it takes a real effort to change that perspective.
> But it is very often valuable to do so. Far too often, I have
> seen various claims of advantages or disadvantages in a given
> system presented as being the result of something "being
> analog" or "being digital," when in fact these concerns had
> nothing to do with what was being considered.

I pretty much agree. It's too bad that some people become upset and
angry when their established mindsets are challenged.

Jerry
--
"The rights of the best of men are secured only as the
rights of the vilest and most abhorrent are protected."
- Chief Justice Charles Evans Hughes, 1927
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Jerry Avins]

CWatters wrote:
> "Jerry Avins" <[email protected]> wrote in message
> news:[email protected]...
>> It seems to me important to agree on criteria for deciding whether a
>> particular circuit or signal is digital or analog
>
> The faster the digital circuit goes the more analog it becomes.

That's a good sig!

--
The faster a digital circuit goes, the more analog it becomes.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Scott Seidman]

"John E. Hadstate" <[email protected]> wrote in news:a9k2h.18885
[email protected]:

> To instantiate or process a digital
> state, it must be encoded into a voltage/current analog.
>

True, but only well enough to differentiate a low from a high, and you can
also build in error correction.

--
Scott
Reverse name to reply

[Steve Underwood]

Jerry Avins wrote:
> Richard Owlett wrote:
>> Bob Myers wrote:
>>
>>> "Jerry Avins" <[email protected]> wrote in message
>>> news:[email protected]...
>>>
>>>> It seems to me important to agree on criteria for deciding whether a
>>>> particular circuit or signal is digital or analog
>>>
>>>
>>> Circuits and signals themselves are neither digital nor
>>> analog, even though we unfortunately do tend to classify
>>> them as such.
>>>
>>
>> I've seen a 7400 series inverter used as an 'op amp'
>> Don't recall why it was done, suspect was just to prove it could be ;/
>
> Lousy choice. The symmetric CD40xx, on the other hand, was well enough
> suited to be used in at least onecommercial product.

If there was a choice you'd use a proper op-amp. You only use these
gates because they are leftovers in a multi-gate package. 74xx devices
were used quite often in semi-analogue roles.

I find it an interesting paradox that in the old days nobody sold single
gate devices. Now simple logic has been reduced to the role of glue, a
number of suppliers make tiny one gate devices.

Steve

[John E. Hadstate]

"Bob Myers" <[email protected]> wrote in message
news:[email protected]...
>
> "John E. Hadstate" <[email protected]> wrote in message
> news:[email protected].. .
>> That is demonstrably incorrect. All circuits that have a
>> physical instantiation are analog, as are the signals
>> that they process.
>
> Well, it all depends on which definition of "analog"
> you're using I guess. From the following comment:
>
>>
>> [snip fairly lucid description of analog encoding]
>>
>
> ...I would have assumed that we were in agreement
> there.

Yes, in terms of your description of what analog means, I
think you were right on target.

> In which case "analog" and "digital" BOTH refer
> to how information is encoded onto a signal, but not
> really the signal itself.

Depends on what you mean by signal. (This conversation is
becoming downright Clintonesque.)

> Elsewhere I have given an example
> of a signal which cannot be unambiguously classified as
> either "analog" or "digital" in the common (and sloppy)
> use of those terms merely by looking at it.

I read it. I thought it was brilliant.

> Given that
> confusion, I am simply proposing that if you really want
> to see what's going on, you think of circuits and signals
> as simply being "electrical" - and leave the words
> "analog"
> and "digital" for use only in pointing to encodings.

I started to make that distinction. Then I thought about
many examples of analog and digital hydraulic and mechanical
circuits and decided to go with the more general concept.

>
> Admittedly, most of us in the industry are VERY used to
> using these terms another way (and I do so myself in many
> cases), and it takes a real effort to change that
> perspective.
> But it is very often valuable to do so. Far too often, I
> have
> seen various claims of advantages or disadvantages in a
> given
> system presented as being the result of something "being
> analog" or "being digital," when in fact these concerns
> had
> nothing to do with what was being considered.
>

I think we are in violent agreement ;-)

[Jerry Avins]

Steve Underwood wrote:
> Jerry Avins wrote:
>> Richard Owlett wrote:
>>> Bob Myers wrote:
>>>
>>>> "Jerry Avins" <[email protected]> wrote in message
>>>> news:[email protected]...
>>>>
>>>>> It seems to me important to agree on criteria for deciding whether
>>>>> a particular circuit or signal is digital or analog
>>>>
>>>>
>>>> Circuits and signals themselves are neither digital nor
>>>> analog, even though we unfortunately do tend to classify
>>>> them as such.
>>>>
>>>
>>> I've seen a 7400 series inverter used as an 'op amp'
>>> Don't recall why it was done, suspect was just to prove it could be ;/
>>
>> Lousy choice. The symmetric CD40xx, on the other hand, was well enough
>> suited to be used in at least onecommercial product.

Sure. You may think of a one-shot as a digital device, but it takes a
fair amount of analog savvy to build one whose pulse width is
independent of duty cycle.

> If there was a choice you'd use a proper op-amp. You only use these
> gates because they are leftovers in a multi-gate package. 74xx devices
> were used quite often in semi-analogue roles.

I recall one audio device that used an entire hex inverter chip as a
stereo headset amplifier.

> I find it an interesting paradox that in the old days nobody sold single
> gate devices. Now simple logic has been reduced to the role of glue, a
> number of suppliers make tiny one gate devices.

I may have a few one-gate RTL packages (six lead, round).

Jerry
--
"I view the progress of science as ... the slow erosion of the
tendency to dichotomize." Barbara Smuts, U. Mich.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Ray Andraka]

Jerry Avins wrote:

>
> Sure. You may think of a one-shot as a digital device, but it takes a
> fair amount of analog savvy to build one whose pulse width is
> independent of duty cycle.
>

As a digital guy, I sure don't consider one-shots digital. By
one-shots, I am referring to those devices that use the physical
characteristics of components (typically capacitance and resistance) to
set a time delay.

The distinction I use in my book (which sadly will probably never be
finished because of the time involved writing it) is that an analog
circuit depends on the physical properties of the components of the
circuit as an integral part of the processing. A digital circuit
processes the signal through a logical or numerical manipulation of the
signal so that the circuit itself is only incidental to the processing.

Clearly, with that definition, one-shots such as the 74123 belong to the
class of analog circuits regardless of whether they were offered as a
component within a digital logic family. The only thing digital about
these parts is the logic family compatible I/O and the simple logic
controls built in to allow the one shot to be operated by and output to
the logic family.

Another circuit that used to be commonly used with digital logic that is
really an analog part is the delay line.

[Jerry Avins]

Ray Andraka wrote:
> Jerry Avins wrote:
>
>>
>> Sure. You may think of a one-shot as a digital device, but it takes a
>> fair amount of analog savvy to build one whose pulse width is
>> independent of duty cycle.
>>
>
> As a digital guy, I sure don't consider one-shots digital. By
> one-shots, I am referring to those devices that use the physical
> characteristics of components (typically capacitance and resistance) to
> set a time delay.
>
> The distinction I use in my book (which sadly will probably never be
> finished because of the time involved writing it) is that an analog
> circuit depends on the physical properties of the components of the
> circuit as an integral part of the processing. A digital circuit
> processes the signal through a logical or numerical manipulation of the
> signal so that the circuit itself is only incidental to the processing.
>
> Clearly, with that definition, one-shots such as the 74123 belong to the
> class of analog circuits regardless of whether they were offered as a
> component within a digital logic family. The only thing digital about
> these parts is the logic family compatible I/O and the simple logic
> controls built in to allow the one shot to be operated by and output to
> the logic family.
>
> Another circuit that used to be commonly used with digital logic that is
> really an analog part is the delay line.

I'd say that a one-shot is digital in intent and analog in execution. I
believe that's true of any physical digital component, just more clearly
evident with circuits that intentionally use Rs and Cs for timing. All
circuits incorporate Rs and Cs, whether intentionally or not. Memory
buses are "digital" too, but modern clock speeds dictate that they be
designed like the broadband transmission lines they really are.

Very few dichotomies are entirely clear. For most, it is possible to
assign most items to one class or the other although the matter is
ambiguous for some near the division. The analog-digital dichotomy puts
the fuzzy dividing line over near one edge. We may use current,
pressure, voltage, fluid flow and other analogs to represent ones and
zeros, but they are all analogs nonetheless. Those ones and zeros exist
in pure form only in out minds. Even marks on paper are analogs of a
sort. We move the division to match a particular purpose. Assuming that
it is fixed hobbles our thoughts.

I began this thread to isolate this discussion from the rancor
developing in another one. I'm pleased to note that it seems to have
succeeded.

Jerry
--
"I view the progress of science as ... the slow erosion of the
tendency to dichotomize." Barbara Smuts, U. Mich.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Bob Myers]

"John E. Hadstate" <[email protected]> wrote in message
news:[email protected]. ..
> Depends on what you mean by signal. (This conversation is becoming
> downright Clintonesque.)

Well, THAT would depend on just what your definition
of "is" is....:-)

But I think at this point we ARE in violent agreement about
pretty much all the real points, and are in danger of starting
a task of rearranging the semantic deck chairs, so I
think I'll quit until something else comes along.

>
>> Elsewhere I have given an example
>> of a signal which cannot be unambiguously classified as
>> either "analog" or "digital" in the common (and sloppy)
>> use of those terms merely by looking at it.
>
> I read it. I thought it was brilliant.

Thanks!

Bob M.

[Ray Andraka]

Jerry Avins wrote:

> Ray Andraka wrote:
>
>> Jerry Avins wrote:
>>
>>>
>>> Sure. You may think of a one-shot as a digital device, but it takes a
>>> fair amount of analog savvy to build one whose pulse width is
>>> independent of duty cycle.
>>>
>>
>> As a digital guy, I sure don't consider one-shots digital. By
>> one-shots, I am referring to those devices that use the physical
>> characteristics of components (typically capacitance and resistance)
>> to set a time delay.
>>
>> The distinction I use in my book (which sadly will probably never be
>> finished because of the time involved writing it) is that an analog
>> circuit depends on the physical properties of the components of the
>> circuit as an integral part of the processing. A digital circuit
>> processes the signal through a logical or numerical manipulation of
>> the signal so that the circuit itself is only incidental to the
>> processing.
>>
>> Clearly, with that definition, one-shots such as the 74123 belong to
>> the class of analog circuits regardless of whether they were offered
>> as a component within a digital logic family. The only thing digital
>> about these parts is the logic family compatible I/O and the simple
>> logic controls built in to allow the one shot to be operated by and
>> output to the logic family.
>>
>> Another circuit that used to be commonly used with digital logic that
>> is really an analog part is the delay line.
>
>
> I'd say that a one-shot is digital in intent and analog in execution. I
> believe that's true of any physical digital component, just more clearly
> evident with circuits that intentionally use Rs and Cs for timing. All
> circuits incorporate Rs and Cs, whether intentionally or not. Memory
> buses are "digital" too, but modern clock speeds dictate that they be
> designed like the broadband transmission lines they really are.
>
> Very few dichotomies are entirely clear. For most, it is possible to
> assign most items to one class or the other although the matter is
> ambiguous for some near the division. The analog-digital dichotomy puts
> the fuzzy dividing line over near one edge. We may use current,
> pressure, voltage, fluid flow and other analogs to represent ones and
> zeros, but they are all analogs nonetheless. Those ones and zeros exist
> in pure form only in out minds. Even marks on paper are analogs of a
> sort. We move the division to match a particular purpose. Assuming that
> it is fixed hobbles our thoughts.
>
> I began this thread to isolate this discussion from the rancor
> developing in another one. I'm pleased to note that it seems to have
> succeeded.
>
> Jerry

Ah, but Jerry, I think perhaps you missed the distinction. The one-shot
depends on the properties of the R's and C's to set up the timing
parameter. In essence, the one shot is comparing a decaying analog
voltage against a reference analog voltage and outputting a digital
signal to indicate whether or not the reference threshold has been
crossed. There is clearly an analog component to this circuit that
would not work the same if the values of the components were changed.

Memory, and other digital circuits that incorporate capacitors and
resistors do not depend on the values of those components to set the
behavior of the circuit. The digital realization could be moved to
another logic foundation (say hydraulics) and it would perform the same
function (albiet, maybe not as fast). The analog circuit however
depends on the characteristics of the components, so moving it to
another technology generally means either finding a component with
equivalent characteristics or modeling the behavior of the replaced
component with something else that mimics the physical characteristics
of the component. See the fundamental difference is the digital is
performing a numerical or logical manipulation of the signal where the
analog is modifying the signal by subjecting it to physical properties
of the materials, which generally is not quantized.

Digital, by design quantizes the analog nature of the underlying
circuit to represent numbers, but fundamentally you are doing numerical
operations rather than relying on the physical properties of a component
to do the processing (decay of a voltage, for example).

[Jerry Avins]

Ray Andraka wrote:
> Jerry Avins wrote:
>
>> Ray Andraka wrote:
>>
>>> Jerry Avins wrote:
>>>
>>>>
>>>> Sure. You may think of a one-shot as a digital device, but it takes
>>>> a fair amount of analog savvy to build one whose pulse width is
>>>> independent of duty cycle.
>>>>
>>>
>>> As a digital guy, I sure don't consider one-shots digital. By
>>> one-shots, I am referring to those devices that use the physical
>>> characteristics of components (typically capacitance and resistance)
>>> to set a time delay.
>>>
>>> The distinction I use in my book (which sadly will probably never be
>>> finished because of the time involved writing it) is that an analog
>>> circuit depends on the physical properties of the components of the
>>> circuit as an integral part of the processing. A digital circuit
>>> processes the signal through a logical or numerical manipulation of
>>> the signal so that the circuit itself is only incidental to the
>>> processing.
>>>
>>> Clearly, with that definition, one-shots such as the 74123 belong to
>>> the class of analog circuits regardless of whether they were offered
>>> as a component within a digital logic family. The only thing digital
>>> about these parts is the logic family compatible I/O and the simple
>>> logic controls built in to allow the one shot to be operated by and
>>> output to the logic family.
>>>
>>> Another circuit that used to be commonly used with digital logic that
>>> is really an analog part is the delay line.
>>
>>
>> I'd say that a one-shot is digital in intent and analog in execution.
>> I believe that's true of any physical digital component, just more
>> clearly evident with circuits that intentionally use Rs and Cs for
>> timing. All circuits incorporate Rs and Cs, whether intentionally or
>> not. Memory buses are "digital" too, but modern clock speeds dictate
>> that they be designed like the broadband transmission lines they
>> really are.
>>
>> Very few dichotomies are entirely clear. For most, it is possible to
>> assign most items to one class or the other although the matter is
>> ambiguous for some near the division. The analog-digital dichotomy
>> puts the fuzzy dividing line over near one edge. We may use current,
>> pressure, voltage, fluid flow and other analogs to represent ones and
>> zeros, but they are all analogs nonetheless. Those ones and zeros
>> exist in pure form only in out minds. Even marks on paper are analogs
>> of a sort. We move the division to match a particular purpose.
>> Assuming that it is fixed hobbles our thoughts.
>>
>> I began this thread to isolate this discussion from the rancor
>> developing in another one. I'm pleased to note that it seems to have
>> succeeded.
>>
>> Jerry
>
> Ah, but Jerry, I think perhaps you missed the distinction. The one-shot
> depends on the properties of the R's and C's to set up the timing
> parameter. In essence, the one shot is comparing a decaying analog
> voltage against a reference analog voltage and outputting a digital
> signal to indicate whether or not the reference threshold has been
> crossed. There is clearly an analog component to this circuit that
> would not work the same if the values of the components were changed.
>
> Memory, and other digital circuits that incorporate capacitors and
> resistors do not depend on the values of those components to set the
> behavior of the circuit. The digital realization could be moved to
> another logic foundation (say hydraulics) and it would perform the same
> function (albiet, maybe not as fast). The analog circuit however
> depends on the characteristics of the components, so moving it to
> another technology generally means either finding a component with
> equivalent characteristics or modeling the behavior of the replaced
> component with something else that mimics the physical characteristics
> of the component. See the fundamental difference is the digital is
> performing a numerical or logical manipulation of the signal where the
> analog is modifying the signal by subjecting it to physical properties
> of the materials, which generally is not quantized.
>
> Digital, by design quantizes the analog nature of the underlying
> circuit to represent numbers, but fundamentally you are doing numerical
> operations rather than relying on the physical properties of a component
> to do the processing (decay of a voltage, for example).

I wasn't thinking of the memory chips themselves, with charges on
capacitors standing in for ones and zeros, but rather the analog nature
of the interconnections, with their transmission delays, characteristic
impedances, and matched terminations. A flip-flop' set-up and hold times
arise from the underlying analog nature of its components. Even the
pulse width of the one-shot is quantized in trinary a way: long enough,
OK, and too short. Otherwise, they wouldn't be useful. (The memory
chip's charges are similarly quantized: in the zero range, trouble, and
in the one range.) I don't see the distinction between a digital and an
analog circuit element as fundamentally more meaningful than the
distinction between a digital and an analog wire.

Jerry
--
"I view the progress of science as ... the slow erosion of the
tendency to dichotomize." Barbara Smuts, U. Mich.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Ray Andraka]

Jerry Avins wrote:

>
> I wasn't thinking of the memory chips themselves, with charges on
> capacitors standing in for ones and zeros, but rather the analog nature
> of the interconnections, with their transmission delays, characteristic
> impedances, and matched terminations. A flip-flop' set-up and hold times
> arise from the underlying analog nature of its components. Even the
> pulse width of the one-shot is quantized in trinary a way: long enough,
> OK, and too short. Otherwise, they wouldn't be useful. (The memory
> chip's charges are similarly quantized: in the zero range, trouble, and
> in the one range.) I don't see the distinction between a digital and an
> analog circuit element as fundamentally more meaningful than the
> distinction between a digital and an analog wire.
>
> Jerry

Yes, I agree that board designers need to take into account the analog
nature of the signal transmission, and I don't think any current media
for digital logic is wholly digital. That said, I guess I am looking at
it from an algorithmic point of view while you are looking at it from a
physical point of view. To me, digital basically means that your
circuit is using numeric methods rather than physical properties to
obtain the desired result.

Granted, you will have to take into account analog effects in doing a
complete digital implementation, but not for the digital algorithm
itself to work. The distinction is that for a digital circuit any
analog behavior is not germane to the algorithm, rather it exists (often
as a hinderance) as an artifact of the implementation. Contrast that
with an analog circuit where those device physical properties are a
necessary ingredient to a functioning design because you are exploiting
those properties to perform the signal processing.

[glen herrmannsfeldt]

Jerry Avins wrote:

> It seems to me important to agree on criteria for deciding whether a
> particular circuit or signal is digital or analog

> One criterion is intended use; there seems to be general agreement about
> that, so I don't address it here. Another criterion is the nature if the
> signal or circuit itself, without reference to intentions. That is the
> topic of this short essay.

I knew someone once who built a low power FM transmitter.
The final output was a 74S04 TTL gate, cheaper than other
100MHz transistors, and works fine in analog mode.

-- glen

[glen herrmannsfeldt]

Jerry Avins wrote:

(snip on open and closed relay contacts)

> You could say the same about a door, but degree matters, especially to
> the obese.

This reminds me of a discussion about how switch (and relay)
contacts usually have some oxide that the electrons have to
tunnel through. There really isn't metal to metal contact.
(Maybe only one atomic layer of oxide, though.)

-- glen

[glen herrmannsfeldt]

Ray Andraka wrote:

(snip)

> Ah, but Jerry, I think perhaps you missed the distinction. The one-shot
> depends on the properties of the R's and C's to set up the timing
> parameter. In essence, the one shot is comparing a decaying analog
> voltage against a reference analog voltage and outputting a digital
> signal to indicate whether or not the reference threshold has been
> crossed. There is clearly an analog component to this circuit that
> would not work the same if the values of the components were changed.

One shots usually have both digital and analog circuitry.
Flip-flops and voltage comparators are both important.

> Memory, and other digital circuits that incorporate capacitors and
> resistors do not depend on the values of those components to set the
> behavior of the circuit. The digital realization could be moved to
> another logic foundation (say hydraulics) and it would perform the same
> function (albiet, maybe not as fast). The analog circuit however
> depends on the characteristics of the components, so moving it to
> another technology generally means either finding a component with
> equivalent characteristics or modeling the behavior of the replaced
> component with something else that mimics the physical characteristics
> of the component.

In real life it gets worse. Besides DRAM, digital systems have used
analog circuitry for a long time. Pass transistors for one example.
There are stories of Cray using long winding PC board paths to delay
signals enough to arrive at the right time. Intel processors
traditionally (at least the 8080 and 8086) have used dynamic logic,
such that they won't run below some clock rate.

> See the fundamental difference is the digital is
> performing a numerical or logical manipulation of the signal where the
> analog is modifying the signal by subjecting it to physical properties
> of the materials, which generally is not quantized.

> Digital, by design quantizes the analog nature of the underlying
> circuit to represent numbers, but fundamentally you are doing numerical
> operations rather than relying on the physical properties of a component
> to do the processing (decay of a voltage, for example).

So DRAM is analog?

-- glen

[Steve Underwood]

glen herrmannsfeldt wrote:
> Jerry Avins wrote:
>
> (snip on open and closed relay contacts)
>
>> You could say the same about a door, but degree matters, especially to
>> the obese.
>
>
> This reminds me of a discussion about how switch (and relay)
> contacts usually have some oxide that the electrons have to
> tunnel through. There really isn't metal to metal contact.
> (Maybe only one atomic layer of oxide, though.)
>
> -- glen
>
I've had corroded switch contacts make a pretty good copper oxide
rectifier. :-)

Steve

[Howard Eisenhauer]

On Fri, 03 Nov 2006 21:07:10 -0800, glen herrmannsfeldt
<[email protected]> wrote:

>Jerry Avins wrote:
>
>> It seems to me important to agree on criteria for deciding whether a
>> particular circuit or signal is digital or analog
>
>> One criterion is intended use; there seems to be general agreement about
>> that, so I don't address it here. Another criterion is the nature if the
>> signal or circuit itself, without reference to intentions. That is the
>> topic of this short essay.
>
>I knew someone once who built a low power FM transmitter.
>The final output was a 74S04 TTL gate, cheaper than other
>100MHz transistors, and works fine in analog mode.
>
>-- glen

I once used a TTL NOR gate as a mixer- worked very well.

Worked so well in fact that not only did I get A+B & A-B outputs I
also got A, B, 2A+B, 2A-B, A+2B, A-2B, 2A+2B, 2A-2B & lottsa various
other stuff :).

H.

[Jerry Avins]

Ray Andraka wrote:
> Jerry Avins wrote:
>
>>
>> I wasn't thinking of the memory chips themselves, with charges on
>> capacitors standing in for ones and zeros, but rather the analog
>> nature of the interconnections, with their transmission delays,
>> characteristic impedances, and matched terminations. A flip-flop'
>> set-up and hold times arise from the underlying analog nature of its
>> components. Even the pulse width of the one-shot is quantized in
>> trinary a way: long enough, OK, and too short. Otherwise, they
>> wouldn't be useful. (The memory chip's charges are similarly
>> quantized: in the zero range, trouble, and in the one range.) I don't
>> see the distinction between a digital and an analog circuit element as
>> fundamentally more meaningful than the distinction between a digital
>> and an analog wire.
>>
>> Jerry
>
> Yes, I agree that board designers need to take into account the analog
> nature of the signal transmission, and I don't think any current media
> for digital logic is wholly digital. That said, I guess I am looking at
> it from an algorithmic point of view while you are looking at it from a
> physical point of view. To me, digital basically means that your
> circuit is using numeric methods rather than physical properties to
> obtain the desired result.
>
> Granted, you will have to take into account analog effects in doing a
> complete digital implementation, but not for the digital algorithm
> itself to work. The distinction is that for a digital circuit any
> analog behavior is not germane to the algorithm, rather it exists (often
> as a hinderance) as an artifact of the implementation. Contrast that
> with an analog circuit where those device physical properties are a
> necessary ingredient to a functioning design because you are exploiting
> those properties to perform the signal processing.

Calling circuits, signals, and systems "digital" is certainly useful
(and I'll keep doing it), but (I think you agree) it describes their use
and design, not their physical nature. I think keeping that distinction
helps me to maintain insight and to remember that technology isn't magic.

A lady brought an old photo of her deceased husband to a photography
studio. She wanted it enlarged and was told that it was no problem.
(Good scanners are cheap nowadays.) She asked if the hat could be
removed, and was told that it would be more difficult, hence expensive.
(Digital photography has made this work wonderfully easy, but only by
comparison.) The photographer then asked what color her husband's hair
had been and which side it had been parted on. "What kind of question is
that?" she asked. "When you take the hat off, you'll know."

Jerry
--
"I view the progress of science as ... the slow erosion of the
tendency to dichotomize." Barbara Smuts, U. Mich.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Michael A. Terrell]

glen herrmannsfeldt wrote:
>
> So DRAM is analog?


Its all done with smoke and capacitors.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

[Steve Underwood]

Michael A. Terrell wrote:
> glen herrmannsfeldt wrote:
>
>>So DRAM is analog?
>
>
>
> Its all done with smoke and capacitors.

They only smoke when overclocked. :-)

Steve

[Michael A. Terrell]

Steve Underwood wrote:
>
> Michael A. Terrell wrote:
> > glen herrmannsfeldt wrote:
> >
> >>So DRAM is analog?
> >
> >
> >
> > Its all done with smoke and capacitors.
>
> They only smoke when overclocked. :-)
>
> Steve


Or if they don't like the electrons you feed them. :(


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

[Ray Andraka]

>> Its all done with smoke and capacitors.
>
>
> They only smoke when overclocked. :-)
>

Naw, it's just you only see the smoke when you do something that lets
the magic smoke out of the package. It's sort of like a genie, once you
let the smoke out, the magic is gone and the part no longer functions.

[Ron N.]

Jerry Avins wrote:
> It seems to me important to agree on criteria for deciding whether a
> particular circuit or signal is digital or analog

At the quantum level, everything might be digital; but above that
level everything looks more analog. However many digital engineers
will only treat anything as analog when dragged kicking and
screaming.

Otherwise, if there exist a useful model of a signal or circuit
which can treat everything as a bunch of "1"'s or "0"'s, and still
predict the systems behavior correctly (within the applications
reliability targets, and when the system is operated within design
contraints), then any of the actual behavior outside of the digital
models is ignored.

So the difference between digital and analog is conscious
ignorance. If the ignorance succeeds, then the circuit or
signal is digital. If there is a failure of this ignorance,
or the system is being operated near the edge of operating
constraints or reliability goals, then analog models are brought
back into the picture to see if they can do better.


IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M

[Jerry Avins]

Ron N. wrote:

...

> So the difference between digital and analog is conscious
> ignorance. If the ignorance succeeds, then the circuit or
> signal is digital. If there is a failure of this ignorance,
> or the system is being operated near the edge of operating
> constraints or reliability goals, then analog models are brought
> back into the picture to see if they can do better.

That seems very cogent to me. Thanks.

Jerry
--
"I view the progress of science as ... the slow erosion of the
tendency to dichotomize." Barbara Smuts, U. Mich.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

[Richard Owlett]

Jerry Avins wrote:

> Ron N. wrote:
>
> ...
>
>> So the difference between digital and analog is conscious
>> ignorance. If the ignorance succeeds, then the circuit or
>> signal is digital. If there is a failure of this ignorance,
>> or the system is being operated near the edge of operating
>> constraints or reliability goals, then analog models are brought
>> back into the picture to see if they can do better.
>
>
> That seems very cogent to me. Thanks.
>
> Jerry

May I give a "counter example"?

Light was once thought to be "continuous" ("analog").
*THEN* photons were "discovered". Particles are "discrete"/"digital".

Please note liberal use of " character.


In other words (as has been stated before), chose the representation
most appropriate to problem.

[Zak]

Steve Underwood wrote:

> If there was a choice you'd use a proper op-amp. You only use these
> gates because they are leftovers in a multi-gate package. 74xx devices
> were used quite often in semi-analogue roles.


Did anyone ever analyse or even draw a schematic of the 'keychain
whistle' devices? When you'd whithle, it would beep back at you to
indicate where it was.

ISTR it used a CD4000 or similar as only active device, and a single
piezo as both mic and beeper.

It would go quite some time on a battery as well. Clever design.



Thomas