[TriLUG] null modem cable?

[Aaron S. Joyner]

Mike Johnson wrote:

> Jason Tower wrote:
>
>> i'm looking for a female db9 to male db25 null modem cable (to 
>> connect my laptop serial port to a sun sparcstation serial port).  if 
>> anyone has one lying around i'd appreciate it.  thanks,
>
>
> Jason,
>
> I always used a db9 to db9 cable, a db9 to db25 adapter, and a null 
> modem adapter.  A little clunky, but easier to find than the cable 
> you're looking for.
>
> Mike

Intrex, null modem cable + gender bender.

Normally, if the people who designed your hardware understood how serial 
ports should be built (DTE is male, DCE is female), then a null modem 
cable should only be needed when the ends couldn't physically be plugged 
into each other (i.e. attempting to connect two female ports together, 
or two male ports together).  That's what the null modem cable you'll 
find at Intrex (or virtually any other null modem device) should have 
the same gender on both ends (in Intrex's case, female - as connecting 
two computers together is the most likely scenario, as opposed to 
connecting two modems together).  So for the strange scenario you're 
suggesting, you'd require both a null modem cable and a gender bender 
(ie. a male <-> male connector).  As a curious question, have you tried 
just plugging the two directly together, or using a regular serial 
extension?  It probably won't work, even though the orientation of the 
connectors implies that it should.  For more information on DTE (Data 
Terminal Equipment) vs DCE (Data Communications Equipment), check out 
the RFCs for RS-232 Serial.

Aaron S. Joyner