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Null Modem Cable

Discussion in 'Hobby Electronics' started by ocular, Aug 6, 2003.

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  1. ocular

    ocular Guest

    Need a DB25M to DB9F Null modem cable that is shielded.
    Can't seem to find one ready made

    I have the DB25M and DB9F connectors and the wiring diagram

    http://www.pbxsoftware.com/winprog/connect.shtml

    What shielded cable should/can I use?

    I already have a DB9F to DB9M serial cable. If I could find a DB9F to
    DB25M Null modem adapter then this would be an alternative.
     
  2. Doug Laidlaw

    Doug Laidlaw Guest

    You have 9 wires running from one to the other according to the site. My
    recollection of a null modem cable is that all 9 wires are not required,
    since some wires link between 2 pins at one end.

    DB25 to DB25 null modem adaptors are available. You can also get null modem
    cables, some with both 9-pin and 25-pin connectors. I would get hold of
    one of these and an appropriate gender changer.

    Doug.
     
  3. Rod Speed

    Rod Speed Guest

    Why ? The whole point of RS232 is
    that its designed to not need shielding.
    Because thats pointless normally.
    You need to say why it has to be shielded to be able to say.
     
  4. ocular

    ocular Guest

    Need to manage Panasonic KXTD816 KSU with programming software.

    Tried non shielded cable and data transfer is not reliable, been advised
    by phone company that shielded cable is needed.

    Can find some overseas supplier of DB9F to DB25M Null modem cables

    http://www.neutronexpress.com/prod.cfm/11245/CABLES_TO_GO/03019/6FT_NULL
    _MODEM_CABLE_DB25M_DB9F

    shipping costs to OZ US$36


    and yes they are made with shielded cable so can't be too pointless.

    www.qconnect.com.au will make such a cable for $20
     
  5. Mike Harding

    Mike Harding Guest

    What is a KXTD816?
    How long is your RS232 cable run? I've used non shielded RS232
    over 100m at 38400.

    Unless you have a long cable run and are in a _very_ noisy
    electrical environment (ie. near an arc welder) I doubt that the
    lack of shielding is your problem. However that's the kind of
    thing manufacturers usually say when they don't know what's
    going on.

    Ensure you're using the correct number of bits and parity is
    correctly set .

    Mike Harding
     
  6. Newsy

    Newsy Guest

    Or try a lower data speed.

    Rod
     
  7. Rod Speed

    Rod Speed Guest

    Thats completely mad, the problem is elsewhere.
    Just the usual stupid overdesign for those stupid enough to buy them.
     
  8. Alan

    Alan Guest

    Yep got to agree. I've been owrking with PBXs for over 20 years, and their
    generally not very fussy. Program NEC at 2400bps using flat ribbon cable a
    couple of meters long without problems. I'd be pulling your existing cable
    apart and checking for dry joints/ bad crimps before I wooried too much
    about sheilding.
     
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