Help Null Modem Cable

Help Null Modem Cable

Post by John Kristof » Tue, 30 Jun 1998 04:00:00




>Can anyone explain to me how to make a "Null modem cable".  I have the pin
>assignment for my serial ports, I just need to be SURE what to connect to
>what.

A good long term solution is to just buy a pre-made cable built to the
specifications you need (i.e. 9-pin male to 25-pin female cross-over 6'
RS-232 cross-over cable).  Most people don't make the typical serial cables
(I would guess that you may need soldering and molding equipment).  Buying
the type you need or using a device as mentioned below is typically much
more practical.

A couple of good alternatives exist if you do not need a permanent cable.
You can purchase a "break-out box" or something like a Micropatch(TM).  A
breakout box offers all the capabilities to monitor and set up a RS-232
connection as needed.  They can cost over $100 for a good one.  A Micropatch
is a small adapter that allows you to wire one side to the other any way you
want.  I think they cost about $20.  These are particularly handy.