Computer Interfacing
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about rs232 cable


 

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keisuke
New User



Joined: 11 Oct 2007
Posts: 1


Oct 11, 2007 3:37 am

hihi.....anyone know how to test whether cable is null modem or direct modem?? what is the difference between those two type of cable?? thanks alot.....
lammert
Site Admin



Joined: 13 Mar 2007
Posts: 145
Location: Netherlands and Kazakhstan

Oct 11, 2007 3:59 pm

Null modem cables differ from normal RS232 cables in the way lines between pins are twisted. The easiest way is to check pin 2 on each side. If both connectors have the same size (both 9 or both 25 pins) and pin 2 of one connector is connected with pin 2 on the other side it is a direct cable, otherwise it is a null modem cable.

When the sizes of both connectors are different (i.e. one is 9 pins and the other 25 pins) the check is a little bit different. If pin 2 on one side connects with pin 2 on the other side the cable is null modem wired, otherwise direct.
Unicorn988
New User



Joined: 03 Mar 2015
Posts: 1


Mar 03, 2015 11:29 am

connectors have the same size (both 9 or both 25 pins) and pin 2 of one connector is connected with pin 2 on the other side it is a direct cable...??



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watson

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