I thought this excellent guide to PC Cables needed a slight update.

The original work is contained in the CABLES1.TXT file by Bill
Becwar and is included in this ZIP file in its entire, unaltered
state.

Below I have included the layouts to the cables I have worked with
recently that might be of help to others.

Taking the disclamer from Bill Becwar, I repeat it below to prevent
any thought that I may be held liable for any problems this guide
may or may not cause you or anyone else.

-----
LEGAL STUFF - This guide is as complete and accurate as I can make
it, however, I can't be responsible for errors, omissions, typing
mistakes, bad downloads, or your dog biting you.  I know that
somebody, somewhere is going to cross a wire.  Best advice if you
want to build one of these cables: Complete the wiring all in one
work session.  Then check the connections, preferably with an
ohmmeter.  Go away for a while and do something else, then return
and CHECK the connections again.  If you have any comments or find
any errors, leave E-Mail to Darrell Bivens on Silver Bullet BBS,
(615) 337-9683 Sweetwater, East Tennessee.  Good Luck!
-----


Null modem cables (Several variations)

The first variation is explained in an excert from the ZIP162 DOC
file.  The ZIP program will allow computer <> computer file
transfers through a null modem cable.  It can even clone itself over
the cable (in case the disk drives are not compatible/working).

I have tried this cable with Central Point Software's DriveMap 1.0
program and Lap Link V 5.0.  It works perfectly.  Also note if you
build a 25 <> 25 pin cable and you need to connect to a 9 pin COM
port that a STANDARD 9F > 25M adapter and/or adapter cable will
connect the correct pins.

I have not tried a 9 <> 9 pin cable using a 25F > 9M adapter.  It
may or may not work.  I don't have an cable of this type to check.


Excert from ZIP162.DOC file:

"----------------------- C. APPROPRIATE SERIAL CABLES ------------------------

     SERIAL NULL MODEM CABLES, in various combinations of 9- and 25-pin 
connectors, are available from a wide variety of sources, and a simple cable 
in the configuration you need (for example, DB9 to DB25 female) should cost 
less than $10 at Radio Shack or many computer stores.  Double-headed null 
modem cables (both 9 and 25 pin on each end) are also made, and would be ideal 
for use with ZIP; I am told that a good source for these is:
     DALCO, 233 Pioneer Blvd, Springboro OH 45066; (800)445-5342

     If you're building or shopping for a cable, you need a "null modem" 
cable, meaning the transmit and receive data lines should be crossed, and the 
signal ground connected straight through.  (The pin numbers depend on whether 
you have a small DB9 or large DB25 connector, see figure.)  No other 
connections should be needed; ZIP uses no hardware handshaking lines.  (NOTE: 
ZIPDUP does require the DTR connections between pins 20/4 and 6.)

        |--COMPUTER 1--|         |--COMPUTER 2--|
         DB9F or   DB25F          DB25F or   DB9F
      pin 2 - - - - 3 - - - - - - - 2 - - - - 3   \ transmit &
          3 - - - - 2 - - - - - - - 3 - - - - 2   / receive data
          5 - - - - 7 - - - - - - - 7 - - - - 5   - signal ground

      pin 4 - - - - 20  - - - - - - 6 - - - - 6 * \
          6 - - - - 6 - - - - - - - 20  - - - 4 *  \handshaking (optional)
          7 - - - - 4 - - - - - - - 5 - - - - 8    /(* required for ZIPDUP)
          8 - - - - 5 - - - - - - - 4 - - - - 7   /

Actually, any serial cable that doesn't work by itself, should work with a 
"null modem adapter" attached.  If available, use a well shielded cable; high 
speed transmissions can be especially susceptible to RF interference."

----------------------------------------------------------------------------


In talking around and asking several Tech. support persons I received
some variations on the null modem cable.  Below are the most to least
common types 'believed' to work.  (Using the chart layout from above)

        |--COMPUTER 1--|         |--COMPUTER 2--|
         DB9F or   DB25F          DB25F or   DB9F
      pin   - - - - 1 - - - - - - - 1 - - - -
          3 - - - - 2 - - - - - - - 3 - - - - 2
          2 - - - - 3 - - - - - - - 2 - - - - 3
          7 - - - - 4 - - - - - - - 5 - - - - 8
          8 - - - - 5 - - - - - - - 4 - - - - 7
          6 - - - - 6 - - - - - - - 20- - - - 4 (As you can see here, pins
          1 - - - - 8 - - - - - - - 20- - - - 4 6 & 8 are jumped together
          4 - - - - 20- - - - - - - 6 - - - - 6 and join the 20 on the
          4 - - - - 20- - - - - - - 8 - - - - 1 other end (both ways)).


        |--COMPUTER 1--|         |--COMPUTER 2--|
         DB9F or   DB25F          DB25F or   DB9F
      pin   - - - - 1 - - - - - - - 1 - - - -
          3 - - - - 2 - - - - - - - 3 - - - - 2
          2 - - - - 3 - - - - - - - 2 - - - - 3
          8 - - - - 5 - - - - - - - 20- - - - 4 (As you can see here, pins
          6 - - - - 6 - - - - - - - 20- - - - 4 5, 6 & 8 are jumped together
          1 - - - - 8 - - - - - - - 20- - - - 4 and join the 20 on the
          4 - - - - 20- - - - - - - 5 - - - - 8 other end (both ways)).
          4 - - - - 20- - - - - - - 6 - - - - 6
          4 - - - - 20- - - - - - - 8 - - - - 1


        |--COMPUTER 1--|         |--COMPUTER 2--|
         DB9F or   DB25F          DB25F or   DB9F
      pin   - - - - 1 - - - - - - - 1 - - - -
          3 - - - - 2 - - - - - - - 3 - - - - 2
          2 - - - - 3 - - - - - - - 2 - - - - 3
          7 - - - - 4 - - - - - - -   - - - -   (4 & 5 jumpered on one end
          8 - - - - 5 - - - - - - -   - - - -   but don't connect thru.)
            - - - -   - - - - - - - 4 - - - - 7 (4 & 5 jumpered on one end
            - - - -   - - - - - - - 5 - - - - 8 but don't connect thru.)
          6 - - - - 6 - - - - - - - 20- - - - 4
          4 - - - - 20- - - - - - - 6 - - - - 6



The above 9 pin connections were 'figured out' using the 9<>25 pin
adapters with the following pinouts.

This is the pin outs for adapters from<>to 9<>25 pin cables.

        |-- 9F <> 25M --|                      |-- 25F <> 9M --|
         DB9F or   DB25M                        DB25F or   DB9M
      pin 1 - - - - 8 - - -                         - - - - 1 - - - -
          2 - - - - 3 - - -                       3 - - - - 2 - - - -
          3 - - - - 2 - - -                       2 - - - - 3 - - - -
          4 - - - - 20- - -                       20- - - - 4 - - - -
          5 - - - - 7 - - -                       7 - - - - 5 - - - -
          6 - - - - 6 - - -                         - - - - 6 - - - -
          7 - - - - 4 - - -                       4 - - - - 7 - - - -
          8 - - - - 5 - - -                         - - - - 8 - - - -
          9 - - - - 22- - -                         - - - - 9 - - - -



Another strange cable I ran into was for a HP Plotter (also applies to
the HP Paint Jet).  A standard serial cable would not work, nor would a
null modem cable.  Before you go out and buy an expensive HP cable try
making your own from one of the following pinouts.


Type I (From a Commercially produced cable/computer store)

        |-- COMPUTER --|   >>>   |--HP Plotter--| (Or Paint Jet)
        *DB9F  or  DB25F   >>>    DB25M
      pin 3 - - - - 2 - - - - - - - 3
          2 - - - - 3 - - - - - - - 2
          8 - - - - 5 - - - - - - - 20
            - - - - 6 - - - - - - - 20
          5 - - - - 7 - - - - - - - 7

* The above 9 pin connections were 'figured out' using the 9<>25 pin
adapters shown above.



Type II (From a Commercially produced cable/computer store)

        |-- COMPUTER --|   >>>   |--HP Plotter--| (Or Paint Jet)
         DB9F  or *DB25F   >>>    DB25M
      pin 1 - - - -   - - - - - - - 4
          2 - - - - 3 - - - - - - - 2
          3 - - - - 2 - - - - - - - 3
          4 - - - - 20- - - - - - - 5
          4 - - - - 20- - - - - - - 6
          5 - - - - 7 - - - - - - - 7
          6 - - - -   - - - - - - - 4
          7 - - - - 4 - - - - - - - 8
          8 - - - -   - - - - - - - 20

* The above 25 pin connections were 'figured out' using the 9<>25 pin
adapters shown above.



Type III (From a Computer store made cable in use 12/6/93)

        |-- COMPUTER --|   >>>   |--HP Plotter--| (Or Paint Jet)
        *DB9F  or  DB25F   >>>    DB25M
      pin   - - - - 1 - - - - - - - 1
          3 - - - - 2 - - - - - - - 3
          2 - - - - 3 - - - - - - - 2
          8 - - - - 5 - - - - - - - 20
          6 - - - - 6 - - - - - - - 20
          5 - - - - 7 - - - - - - - 7
          4 - - - - 20- - - - - - - 5
          4 - - - - 20- - - - - - - 6

* The above 9 pin connections were 'figured out' using the 9<>25 pin
adapters shown above.



Type IV (From a Home made cable in use 12/6/93)

        |-- COMPUTER --|   >>>   |--HP Plotter--| (Or Paint Jet)
         DB9F  or *DB25F   >>>    DB25M
      pin 1 - - - -   - - - - - - - 1
          2 - - - - 3 - - - - - - - 2
          3 - - - - 2 - - - - - - - 3
          4 - - - - 20- - - - - - - 5
          4 - - - - 20- - - - - - - 6
          5 - - - - 8 - - - - - - - 7
          6 - - - - 6 - - - - - - - 20
          8 - - - - 5 - - - - - - - 20


* The above 25 pin connections were 'figured out' using the 9<>25 pin
adapters shown above.




DOS V 6.0 (and Central Point Software's PCTools 8.0 w/ Drive Map 1.0)
introduced the ability to use a parallel cable (Printer port to Printer
port cable) to connect two PCs together and share drives.  The pin outs
for the "LINK DOS 6.0" cable follows:


        |--COMPUTER 1--|         |--COMPUTER 2--|
             DB25M                    DB25M
      pin     2 - - - - - - - - - - - - 15
              3 - - - - - - - - - - - - 13
              4 - - - - - - - - - - - - 12
              5 - - - - - - - - - - - - 10
              6 - - - - - - - - - - - - 11
              10- - - - - - - - - - - - 5
              11- - - - - - - - - - - - 6
              12- - - - - - - - - - - - 4
              13- - - - - - - - - - - - 3
              15- - - - - - - - - - - - 2





Most serial port connections only require a few wires to be connected.
The most common types of connections only require:

        |-- COMPUTER --|         |--  DEVICE  --|
        *DB9F  or  DB25F          DB25M  or  DB9F*
      pin   - - - - 1 - - - - - - - 1 - - - -
          3 - - - - 2 - - - - - - - 2 - - - - 3
          2 - - - - 3 - - - - - - - 3 - - - - 2
          7 - - - - 4 - - - - - - - 4 - - - - 7
          8 - - - - 5 - - - - - - - 5 - - - - 8
          6 - - - - 6 - - - - - - - 6 - - - - 6
          5 - - - - 7 - - - - - - - 7 - - - - 5
          1 - - - - 8 - - - - - - - 8 - - - - 1
          4 - - - - 20- - - - - - - 20- - - - 4


* The above 9 pin connections were 'figured out' using the 9<>25 pin
adapters shown above.



Full pin 25M <> 25F cables have all pins connected straight through:

                  25F        <>        25M

                   1                    1
                   2                    2
                   3                    3
                  ...                  ...
                  23                   23
                  24                   24
                  25                   25

thus making extension cables for either serial or printer cable
connections.



Serial cables that have both Male ends or both Female ends are strange.
The pins are connected from<>to the same pin number on the other end
(1-1, 2-2, 3-3, ... 25-25) but since the gender is the same on both ends
these cables are not extension cables but actually CROSS the wires. If
you were to plug two 'same gender' cables to each other thus making a
connection like:

                  25F  >  25F<>25M  >  25M

                   1      25    25      1
                   2      24    24      2
                   3      23    23      3
                  ...     ...   ...    ...
                  23       3     3     23
                  24       2     2     24
                  25       1     1     25

you would have actually created an extension cable.



I hope this information serves to help some others that were in search of
answers about computer cables.  If you do find any errors in the above
text please let me know.

Darrell Bivens  Silver Bullet BBS       (615) 337-9683
Compiled 12/6/93

*the end*
