Subject:
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Re: Re[2]: phone cord length
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Fri, 7 Mar 1997 05:39:12 GMT
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Original-From:
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Fred G. Martin <fredm@media.mit.eduNOSPAM>
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Viewed:
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2079 times
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thx for correcting my wording. e.g., instead of saying "half twist" i
should say "straight through". anyhow, we agree on the definition of
what is a phone cable and what is not a phone cable, we just have a
different way of illustrating it.
the point stands: only phone cable (cross-over as alan calls them)
must be used with Handy Board.
-fred
In your message you said:
> Sorry Fred, but I must respectfully disagree.....
>
> Fred G. Martin wrote:
> (snip)
> >
> > BTW, while we're on the topic of serial and phone cords, please be
> > VERY CAREFUL when swapping phone cords. The Handy Board requires a
> > telephone-style cord. Many of us have network-style RJ11 cords lying
> > around our offices, which have a half twist in their wiring.
>
> Actually it is phone cords which are the crossover type. Use of a patch-
> cord tester confirms this. I am not familiar with any RJ11 network cables,
> but I know that the standard line cord for a phone is a crossover cable.
> >
> > Network-style RJ11 cables CANNOT, SHOULD NOT, and BETTER NOT be used
> > with Handy Boards.
>
> This is still true, since the effect of using the wrong one is the same.
> >
> > If you use a network style cable, you invert the power and ground
> > connections, which blows up the 47 ohm charge resistor on your serial
> > interface board, along with potential for greater damage.
> >
> > Here is how you tell if you have a telephone-style or network-style
> > RJ11 cable. (snip)
>
> You actually need to put the RJ11 plugs side by side, so they are oriented
> the same way, to see whether they are straight through or crossover. This
> way you see wire color for pin 1 on each end and pin 2, pin 3, etc.
>
> +-----------+ \
> -----------------|black ====| Pin 1 \
> |red ====| Pin 2 \
> |green ====| Pin 3 \
> -----------------|yellow ====| Pin 4 \
> +-----------+ \
> ----- straight-through cable
> +-----------+ /
> -----------------|black ====| Pin 1 /
> |red ====| Pin 2 /
> |green ====| Pin 3 /
> -----------------|yellow ====| Pin 4 /
> +-----------+ /
>
>
> +-----------+ \
> -----------------|black ====| Pin 1 \
> |red ====| Pin 2 \
> |green ====| Pin 3 \
> -----------------|yellow ====| Pin 4 \
> +-----------+ \
> ----- cross-over (phone) cable
> +-----------+ /
> -----------------|yellow ====| Pin 1 /
> |green ====| Pin 2 /
> |red ====| Pin 3 /
> -----------------|black ====| Pin 4 /
> +-----------+ /
>
> Best regards,
> Alan
>
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Message is in Reply To:
 | | Re: Re[2]: phone cord length
|
| Sorry Fred, but I must respectfully disagree..... Fred G. Martin wrote: (snip) (...) Actually it is phone cords which are the crossover type. Use of a patch- cord tester confirms this. I am not familiar with any RJ11 network cables, but I know that (...) (28 years ago, 7-Mar-97, to lugnet.robotics.handyboard)
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