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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Tue, 4 Mar 1997 14:15:21 GMT
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Original-From:
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Fred G. Martin <fredm@/antispam/media.mit.edu>
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Viewed:
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1979 times
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> TTL does NOT go down that line, it is RS232 which is commonly used at
> up to 50 feet. However, you might need to use a shielded cable if you
> use a lead longer than about 10 feet.
No, that is wrong; the RS232 is converted to TTL at the serial
interface board, so you do have TTL on the phone cord.
In any event, I would guess that 50 ft. would not be a problem; we're
talking about 9600 baud here which is pretty slow.
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.
Network-style RJ11 cables CANNOT, SHOULD NOT, and BETTER NOT be used
with Handy Boards.
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. Hold the two ends together, metal contact side up, as if
you were trying to plug them into each other.
Then look at the wiring colors. On a telephone cable, each color
should line up with itself on the other end.
On a network cable, the colors are inverted.
See the diagrams for clarification. Again, please, please, PLEASE!
be careful about this and do not use network cables with your Handy
Board.
-Fred
TELEPHONE STYLE WIRING
+---------------+ +---------------+
--------+ yellow =======+ +======= yellow +--------
+ green =======+ +======= green +
+ red =======+ +======= red +
--------+ black =======+ +======= black +--------
+---------------+ +---------------+
NETWORK STYLE WIRING
+---------------+ +---------------+
--------+ yellow =======+ +======= black +--------
+ green =======+ +======= red +
+ red =======+ +======= green +
--------+ black =======+ +======= yellow +--------
+---------------+ +---------------+
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Message has 1 Reply:
 | | Re: Re[2]: phone cord length
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| 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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Message is in Reply To:
| | Re[2]: phone cord length
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| TTL does NOT go down that line, it is RS232 which is commonly used at up to 50 feet. However, you might need to use a shielded cable if you use a lead longer than about 10 feet. Richard (28 years ago, 4-Mar-97, to lugnet.robotics.handyboard)
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