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Why do we have cross-over cables.

F

FatBytestard

Jan 1, 1970
0
Some other clever fellow figured out how to send voice signals through the
wires - voila! The telephone.


That person was NOT A. G. Bell, however.
 
F

FunkyPunk FieldEffectTrollsistor

Jan 1, 1970
0
Rich Grise wrote:

[snip]

Maybe it would be easier to explain to Sylvia that the
reason we have cross-over cables is because cross-under
cables are too expensive to build.
Have not seen anything from her today. Perhaps *she* has crossed over.
 
F

FatBytestard

Jan 1, 1970
0
Sure it was, he just wasn't the only one or necessarily the first.

Wrong. The INVENTOR was Meucci, and that was DECADES before Bell ripped
him off. Bell was a thief that had huge research backing.
Exactly who invented the telephone first is largely a question of how you
define "telephone"

You're an idiot.
and whether or not you want to trust people who might have
built such a device but didn't document it for posterity...

You're a total retard that obviously has ZERO knowledge of the
historical facts.
 
D

David Segall

Jan 1, 1970
0
She probably is. And with a small group of callers making a lot of
calls to each other it is likely that none of them will ever get
through. Everyone will get the engaged signal because the called party
is dialing someone else.
 
D

David Segall

Jan 1, 1970
0
Obviously, I think she is right in this sub-thread. I also tend to
agree with her original post although others have explained why,
historically, a crossover cable was not standard and why there was a
distinction between terminal and communication equipment.

The only point I might disagree with her on is the assumption that
"this situation persists". Modern interfaces, like USB, use a single
pair of wires for communication which avoids the problem.
 
A

AnimalMagic

Jan 1, 1970
0
Remember TCNS? I think it was token ring. It had hubs all over the
place.

Thomas Conrad Network Systems.

I remember Tandy's 'Arcnet' at 150kb/s (small 'b'). :)
 
A

AnimalMagic

Jan 1, 1970
0
Obviously, I think she is right in this sub-thread. I also tend to
agree with her original post although others have explained why,
historically, a crossover cable was not standard and why there was a
distinction between terminal and communication equipment.

A cross-over cable most certainly WAS and IS the standard for attaching
two like terminals through this interface (serial)

When will you grasp the concept, dolt?
 
A

AnimalMagic

Jan 1, 1970
0
The only point I might disagree with her on is the assumption that
"this situation persists". Modern interfaces, like USB, use a single
pair of wires for communication which avoids the problem.


It is an entirely different schema altogether. Wake up.
 
S

Sylvia Else

Jan 1, 1970
0
It's not really relevant anyway. Neither a token ring, now Ethernet's
backoff approach, can work before it's been established which wires are
which.

There may be a standard that describes the process of identifying the
wires. Whether there is is what I asked.

Sylvia.
 
J

Jasen Betts

Jan 1, 1970
0
Just means those pins would be tied to ground. This would have required
more than the 9 pins on modern serial ports, but would have been easily
done with the original 25 pin standard.


Did something similar with a telephone in my teens, by pulsing the
handset rest.

IIRC it was used in "War Games" (1983)
 
J

Jasen Betts

Jan 1, 1970
0
No luck about it. Make-and-break dialing STILL works.

Not all modems provided electronic control of the "hook switch" (i
forget the correct term) if you were lucky you had one that did.
 
S

Sylvia Else

Jan 1, 1970
0
Jasen said:
there's not such thing,

derive the timimngs from the mac address

Helps if there's a standard that says how, which was my original question.

Sylvia.
 
S

Sylvia Else

Jan 1, 1970
0

Typo. Should have been obvious.

Sometimes. Sometimes not.

If you know of a standard, then why not provide a reference?

Sylvia.
 
D

David Segall

Jan 1, 1970
0
AnimalMagic said:
A cross-over cable most certainly WAS and IS the standard for attaching
two like terminals through this interface (serial)

You seem to have missed the point of the OP's question. You are
excused because you are of an age when an RS232 or Centronics
interface was normal.

As other posters have pointed out it was cheaper to manufacture
straight through cables and in those days there was a clear
distinction the devices at each end of a cable. Pin n of one device
could reasonably be defined as a receiver and Pin n of the "other"
device could be defined as a transmitter. In the last thirty years
that has changed and today it is preferable to treat all devices as
peers.

The OP wanted to know why the distinction between devices existed
rather than _always_ connecting them with a crossover cable. It was a
perfectly reasonable question and she has been provided with sensible
answers by those who managed to understand it.
 
D

David Segall

Jan 1, 1970
0
There may be a standard that describes the process of identifying the
wires. Whether there is is what I asked.

I don't think it requires a "standard" to identify the wires. A NIC
must be able to identify a valid packet so swapping two wires until it
does so is not a demanding task now that a microprocessor is
incorporated on every device.
 
S

Sylvia Else

Jan 1, 1970
0
David said:
I don't think it requires a "standard" to identify the wires. A NIC
must be able to identify a valid packet so swapping two wires until it
does so is not a demanding task now that a microprocessor is
incorporated on every device.

I was thinking that a standard would be required that specified the
delays, or the means of calculation of the delays, to be used between
trying different combinations, so as to avoid the situation where two
NICs undermine each other's attempts to find a working combination.

Sylvia.
 
D

David Segall

Jan 1, 1970
0
Sylvia Else said:
I was thinking that a standard would be required that specified the
delays, or the means of calculation of the delays, to be used between
trying different combinations, so as to avoid the situation where two
NICs undermine each other's attempts to find a working combination.

I think you will find what you are looking for in "IEEE 802.3 LAN/MAN
CSMA/CD Access Method"
<http://standards.ieee.org/getieee802/802.3.html> but I have not read
it.
 
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