Null vs Straight Data Cable

lothario · 12-23-2007, 10:06 PM

I have a few older serial cables.
M to F
M to M
F to F

How can you tell if a serial cable is:
a Null Data Cable
OR
a Straight Data Cable

I don't have access to any kind of testing equipment.

Simon Bridge · 12-23-2007, 10:21 PM

null cables normally have "null" written on it. Are these rs232 cables?

lothario · 12-23-2007, 10:29 PM

These are 9-pin cables.
There is nothing written on these cables.
They look very similar.
But they are Null or Straight.
I was told these were used for programming serial devices.

Simon Bridge · 12-23-2007, 10:53 PM

Serial cables - they are most likely straight.
A null serial cable for rs232 is like a crossover cable for cat5.
For the same reason, they are clearly labeled.

Of course, you can test it out with a modem - you cannot access a modem with a null cable.