misunderstandings that seem inexplicable at the time

"Roderick Stewart" wrote in
message .myzen.co.uk...
In article , Andy Champ wrote:
I've never heard the term "mirror" used for a second screen that looks
like the first. It's always "clone". And I've worked professionally in
computers for more years than I care to admit in public.

My understanding of the term "mirror" is that it's a device you use to see
the screen of a telly while you're fumbling with its innards.

Rod.
--
Virtual Access V6.3 free usenet/email software from
http://sourceforge.net/projects/virtual-access/


When I were a lad I used a mirror to check frame collapse faults on b&w
405-line tellies.

If there was just a thin white line across the middle of the c.r.t. and you
wobbled the mirror at the right speed you could 'reassemble' the vertical
picture by looking in the mirror - therefore proving the fault was in the
frame circuitry.

Happy Days!

"Bill Wright" wrote in message
...

"Roderick Stewart" wrote in
message .myzen.co.uk...
I've had this many times, even when failure to describe the fault has
taken
place over the phone, yet there appears to be an assumption amongst the
technically ignorant that those in the know have some occult method of
divination that we use to diagnose faults without the need for any other
information than "doesn't work" or "broken".

In days of yore people would send a child round to the TV shop for a
'picture valve'.


and, as often as not, came back with an EY51 (or, somewhat later, a PY81)
which was frequently the cause of 'no picture' !
I think I still have a couple in the attic somewhere.

Kenneth

"Petert" wrote in message
...
On Sun, 28 Sep 2008 11:24:33 +0100, Owain
wrote:

Dave Plowman (News) wrote:
My Fluke DVM gives a warning at approx 30 volts. I've never quite worked
out why...

Anything above 30V is probably Dangerous. I think the lowest recorded
voltage for electrocution was 38V?

Owain
It's not the voltage that kills you - 15mA is all that's required (I
think)
--
Cheers

Peter

I was taught that it was the volts that jolts but the mills that kills!

On 28/09/2008 22:04, David Butler wrote:

I was taught that it was the volts that jolts but the mills that kills!

It is, but you need sufficient volts to push the mills.

Bill Wright wrote:
"Roderick Stewart" wrote in
message .myzen.co.uk...
I've had this many times, even when failure to describe the fault has
taken
place over the phone, yet there appears to be an assumption amongst the
technically ignorant that those in the know have some occult method of
divination that we use to diagnose faults without the need for any other
information than "doesn't work" or "broken".

In days of yore people would send a child round to the TV shop for a
'picture valve'.

Bill



And before everybody got them new-fangled goggle boxes, the request was
for a 'power valve'!

Terry

Terry Casey wrote:
Bill Wright wrote:
"Roderick Stewart" wrote
in message
.myzen.co.uk...
I've had this many times, even when failure to describe the fault has
taken
place over the phone, yet there appears to be an assumption amongst the
technically ignorant that those in the know have some occult method of
divination that we use to diagnose faults without the need for any other
information than "doesn't work" or "broken".

In days of yore people would send a child round to the TV shop for a
'picture valve'.

Bill



And before everybody got them new-fangled goggle boxes, the request was
for a 'power valve'!

Terry

In our wireless, that was probably the KT61 (which provided the 'power'
to the loudspeaker) or, occasionally, the U52 (I think that's right -
never did get on with Marconi valve numbering) which, of course,
provided all the (HT) power!

Come to think of it, when I was very small and the wireless went wrong,
I'm not so sure that it wasn't the nice man from Noad's down the road
who told my mum that the problem was the 'power valve' (again!) ...

.... which begs the question of whether it was repairmen talking down to
women (who couldn't possibly be expected to understand these technical
things) that caused this particular problem in the first place.

After all, in those days, men went to work while 'housewives' stayed at
home. A repairman probably only saw a man on rare occasions.

Terry

"Andy Wade" wrote in message
...
John Rumm wrote:

A good example being how the the wiring regs talk about "Low Voltage"
meaning anything 500V or lower.

In the interest of the high standards of accuracy and pedantry that
readers of this group have come to expect, I'd like to point out that:

- 'low voltage' means a nominal voltage exceeding extra-low voltage (ELV)
but but not exceeding 1,000 volts between conductors or 600 volts to earth
for AC, or 1,500/900 volts for DC;

- ELV in turn means a nominal voltage not exceeding 50 V for AC or 120 V
for DC, whether between conductors or to earth.

Most people would probably not think of mains voltage as "low".

This is true. There are plenty of similar examples. The measurement of
brickwork comes to mind - a 9-inch brick wall is one brick thick, not two.

That might explain why all the garden walls around here fall over if you
breathe on them.

--
Max Demian

"John Rumm" wrote in message
et...
Mike Henry wrote:
In , "Dave Plowman (News)"
wrote:

In article ,
John Rumm wrote:
However, I still can't see how you can describe a second display as a
mirror unless it is at least displaying the same image... e.g. plugging

It would also have to reverse the image too, making it useless, to be
called a mirror.

Well, I could understand the phrase being used in that way for this
application. Mirror is used in a number of places in computer technology -
and does not always imply any alteration to the presentation. So a hard
drive mirror (i.e. part of a RAID system) one drive is an exact copy of
the other. A web site, could be mirrored - its content duplicated on
another server etc.

a monitor into the VGA port on many laptops would allow the external
screen to show the same as the internal - that you could call a mirror.
That's what I'd have thought - a 'mirror' is used in IT parlance for a
site that offers an alternative source of the same downloads.

...because it is conveying the fact that changes to the first site also
happen on the mirror site. Just like when you stand at a mirror and move
your arm, the arm in the mirror moves too.

However a mirror in the visual image sense not only shows a copy of
whatever it is reflecting, but it reverses the image. If you have two

That only depends on from where you are looking... after all, why do
mirrors turn images around, but not upside down? ;-)

Actually it depends on the symmetry of the human body. The actual reversal
is front to back - but the easiest mental transformation of match the image
in the mirror is to swing the body 180 degrees on a vertical axis - which
reverses the left and right hands.

--
Max Demian

The message
from J G Miller contains these words:

On Sun, 28 Sep 2008 13:48:37 +0100, Dave Plowman (News) wrote:
Only a loss less one can truly be called compression.

So is the term "lossy compression" a contradiction or an oxymoron?

http://en.wikipedia.ORG/wiki/Lossy_data_compression

It's worth keeping in mind that "lossy compression" can, legitimately,
be taken to its extreme (_all_ of the data being discarded) in certain
circumstances. One such example being an intelligent disk cloning tool
that produces compressed partition images which, effectively, discards
all of the data contained in certain files.

These files are, typically, the page file and (if it exists) the hyber
file on a windows boot/system partition. In this case merely recording
the name and the size of such files within the compressed image archive
suffices since such files become stale on shutdown and are fully
refreshed at each full boot up (a full shutdown being assumed or
asserted by the disk cloning software).

The choice of compression algorithm is decided by the nature of the
data and whether an exact duplicate or a reasonable approximation to the
original is required upon restoring the archive.

--
Regards, John.

Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

In article en.co.uk,
Roderick Stewart wrote:
In article , Bill Wright


I've had this many times, even when failure to describe the fault has
taken place over the phone, yet there appears to be an assumption
amongst the technically ignorant that those in the know have some
occult method of divination that we use to diagnose faults without the
need for any other information than "doesn't work" or "broken".

Yes. I've also experienced a similar misapprehension. Back in ancient days
when I worked as a design engineer I once had a conversation with a company
director about developing equipment like audio power amps, etc.

His idea was that it was a simple routine process of building a predictable
circuit and choosing devices out of a catalogue. Sort of a 'painting by
numbers' approach where you just followed a set of rules.

I tried to explain that - unless you just wanted something with medioce
performance or a clone of something - it did require rather more insight,
experimentation, etc, than that. And that it did require skill, experience
and judgement as there are many valid options, each with their own
advantages and drawbacks to juggle. Thus often a slow and difficult process
if you wanted the result to be outstandingly good.

But I don't think he understood. Like the examples you quote, many people
seem to assume that any science or engineering is some kind of 'mystic
lore' that you learn from a book (or are born with), and either know or
not.

I was always amused by the 'two cultures' idea. Those who wrote about it
seemed to be 'arts types' who assumed they and 'technical types' were
totally different. However my experience has been that a large number of
the engineers and scientists I have met have also been keen amateur
musicians, or interested in 'arts' of all kinds. So the 'two cultures'
seems to be "those who have a clue about technical matters" and "those who
regard it as mystic law - perhaps for a lower class to deal with". :-)

I also still recall fondly a highly regarded prof of physics who became
very angry with me that I was teaching soldering to physics undergrads. He
shouted, "but that's for *technicians*, you shouldn't be teaching that to
undergrads!" So maybe even in the "two cultures" there are some
subdivisions. ;-

Slainte,

Jim

--
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