Null Modem Wiring Schematics

From gjohnson@dream.season.com Mon Oct 28 09:59:58 1996
Newsgroups: comp.terminals
Subject: Pick a number of wires, almost any number . . .
Date: 23 Oct 1996 22:13:28 GMT

During my search for the best thing to do with six wires I helped someone that only had three and got the following response, which might be interesting to readers here.

--
Gary Johnson "Rosebud . . ."
gjohnson@season.com <a href="http://www.epic.org/privacy/wiretap">Freedom?</a>

CAMPAIGN '96: Juck 'em if they can't fake a toke.

From: Francesco Potorti` <F.Potorti@cnuce.cnr.it>
Newsgroups: comp.os.linux.networking
Subject: Re: TCP/IP over null modem?

gjohnson@dream.season.com (Reality is a point of view) writes:

I wish I knew which connections were best when there are six wires available.

I have this note. I copied it from various sources. The only one I really tried is the last one, to be used while connectin two PCs with the DOS program whose name I can't remember (standard with msdos > 5.0)

          7 wires null modem connections
            for V24 protocol on RS-232

              DTE               DTE

        2     [>]------\ /------[<]     2       TX
              [ ]       \       [ ]
        3     [<]------/ \------[>]     3       RX
              [ ]               [ ]
        4     [>]-\           /-[<]     4       RTS
              [ ] |           | [ ]
        5     [<]-+---\   /---+-[>]     5       CTS
              [ ]      \ /      [ ]
        6     [<]----\  /  /----[>]     6       DSR
              [ ]     \/ \/     [ ]
        7     [-]-----/\-/\-----[-]     7       GND
              [ ]    /  \  \    [ ]
        8     [<]---/  / \  \---[>]     8       DCD
              [ ]     /   \     [ ]
        20    [>]----/     \----[<]     20      DTR
          3 wires null modem connections
            for V24 protocol on RS-232

              DTE               DTE

        2     [>]------\ /------[<]     2       TX
              [ ]       \       [ ]
        3     [<]------/ \------[>]     3       RX
              [ ]               [ ]
        4     [>]-\           /-[<]     4       RTS
              [ ] |           | [ ]
        5     [<]-/           \-[>]     5       CTS
              [ ]               [ ]
        6     [<]-\           /-[>]     6       DSR
              [ ] |           | [ ]
        7     [-]-|-----------|-[-]     7       GND
              [ ] |           | [ ]
        8     [<]-+           +-[>]     8       DCD
              [ ] |           | [ ]
        20    [>]-/           \-[<]     20      DTR

Null modem on the MISCO catalogue (DTE)

DTE DTE

        1     [-]---------------[-]     1       GND
              [ ]               [ ]
        2     [>]------\ /------[<]     2       TX
              [ ]       \       [ ]
        3     [<]------/ \------[>]     3       RX
              [ ]               [ ]
        5     [<]-\           /-[>]     5       CTS
              [ ] |           | [ ]
        6     [<]-\           /-[>]     6       DSR
              [ ] |           | [ ]
        7     [-]-|-----------|-[-]     7       GND
              [ ] |           | [ ]
        8     [<]-+----\ /----+-[>]     8       DCD
              [ ]       \       [ ]
        20    [>]------/ \----\-[<]     20      DTR

Null modem on the MISCO catalogue (DCE)

DCE DCE

        1     [-]---------------[-]     1       GND
              [ ]               [ ]
        2     [>]------\ /------[<]     2       TX
              [ ]       \       [ ]
        3     [<]------/ \------[>]     3       RX
              [ ]               [ ]
        4     [>]-----\   /-----[<]     4       RTS
              [ ]      \ /      [ ]
        5     [<]----\  \  /----[>]     5       CTS
              [ ]     \/ \/     [ ]
        6     [<]-----/\ /\-----[>]     6       DSR
              [ ]       \       [ ]
        7     [-]------/-\------[-]     7       GND
              [ ]     /   \     [ ]
        20    [>]----/     \----[<]     20      DTR

Null modem for PC

DCE DCE

        2     [>]------\ /------[<]     2       TX
              [ ]       \       [ ]
        3     [<]------/ \------[>]     3       RX
              [ ]               [ ]
        4     [>]------\ /------[<]     4       RTS
              [ ]       \       [ ]
        5     [<]------/ \------[>]     5       CTS
              [ ]               [ ]
        6     [<]-----\   /-----[>]     6       DSR
              [ ]      \ /      [ ]
        7     [-]-------\-------[-]     7       GND
              [ ]      / \      [ ]
        20    [>]-----/   \-----[<]     20      DTR

--

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