Re: RS485 is bidirectional does it mean it is fullduplex?

floyd@xxxxxxxxxx (Floyd L. Davidson) wrote:
>"Paul E. Bennett" <peb@xxxxxxxxxxxxxxxxxx> wrote:
>>Floyd L. Davidson wrote:
>>> The longest run on an aircraft carrier, or a super tanker, is
>>> short. More than 3 miles is considered "long" in general,
>>> though specifically that may not always be the case.
>>
>>The ships themselves may not be that long but by the time you consider the
>>routes that some of those cables take to get from one end to the other then
>>you should not be surprised that there can be single runs that are of the
>>order of 7km. Then you think about the number of bulkhead feedthroughs and
>>the mind begins to boggle at the number of clamp-down points that the cable
>>sheath has to be pared away, ferrules fitted and boots shrunk down.
>
>I don't know. But that sounds like more of your imagination. A
>7km run is a lot of twisting back and forth to do... (However,
>it does happen that I *can* verify that, and will.)

I did in fact check with someone who spent a few years on an
aircraft carrier. The above is a little too much imagination.

Aircraft carriers are up to 1,100+ feet in length. He figured
the longest loop on the ship would be the "sound powered phone",
but can't imagine that having much more total cable than maybe
twice the length of the ship (I suggest three times, and he
shrugged).

The longest actual loop would be a looped back data circuit
between the stern located approach radars and the bow based
command center. His flat statement was "twice the length of
the ship". No weaving through many ups and down on the way
either, a pretty much straight shot stem to stern.

When I told him the discussion was about the possibility
of a 7 km loop on a ship, he looked at me like I was nuts.

So we talked about ground differentials, and that added another
interesting perspective. His eyes lit up a the mention, and he
said most people have no idea how big a battery that steel hull
is, or how much voltage it generates just sitting in salt water.
As to ground differentials, "*Lots* of voltage!" So I asked how
much, 10's or 100 Volts, or what.

He said, "Oh, I don't know exactly, maybe 30 volts!"

Of course he thought the whole discussion of RS-485 was a
useless endeavor, and just dumped any reference to it in favor
of fiber optics.

--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@xxxxxxxxxx
.

Relevant Pages

  • Congratulations Florida - Oriskany Sunk Today
    ... Aircraft Carrier Sunk in Gulf of Mexico to Create Artificial Reef ... Korean and Vietnam War veterans aboard a flotilla of 300 charter boats ... an acrid smell hung in the air near the ship. ...
    (rec.scuba)
  • Re: Why -Shinano, Lex. Sara. - Royal Oak
    ... That doesnt jibe with the account given by the Archerfish ... Within an hour the target was identified as an aircraft carrier, ... This move put the ship ... Did not head for land or any nearby port or yard. ...
    (sci.military.naval)
  • Re: OT: Unsolicted Email from NG Participants
    ... boarding your ship? ... Have you ever seen an aircraft carrier or know anything about the technology onboard a carier or its compliment of aircraft and other ships? ... Your imaginary boarding party would never get there. ... for Steve. ...
    (microsoft.public.windowsxp.general)
  • Re: Problem with Fermi-Walker Transport in the Physics FAQ file
    ... supply all the illustrations that are left to the imagination of the ... curve is the same function with K=1. ... are shifted left by a different constant x for each ship. ... "Relativistic particle dynamics" ...
    (sci.physics.relativity)
  • Re: Military Ships Sending AIS
    ... nuclear-powered aircraft carrier. ... Stennis was steaming north, about 60NM offshore of San Francisco, on her way ... The Nimitz-class supercarriers are a line of nuclear-powered aircraft ... Malaysia) that denoted itself as a carge ship. ...
    (rec.boats.electronics)