Question 1

What is the pin out?

Accepted Answer

The pinout for the SCNM9FF2MBK is the following:
1-1
2-3
3-2
4-6
5-5
6-4
7-8
8-7
9-9
Shell-Shell

Malcolm, StarTech.com Support

Question 2

Bought this cable to communicate between to systems. It worked for about 20 minutes then stopped completely. Is this due to not having full handshake?

Accepted Answer

That’s going to be hard to figure out. 
There are two similar cables. 
One a straight through and the other is a reverse. 
If you have an Ohm meter then I would check the pin out to see if you have a break in the cable. 
Since there are no electrical components involved I would be inclined to suspect a solfware setting issue. So if the cable hasn’t been damaged then I would check the solftware angle first. 
The other issue is that you may have the wrong cable but if it was working before then software is my best guess. 
Null modem cable has the transmit and receive pins are cross linked. So check out your cable, they look the same, one cross linked and one straight-through.

Question 3

What is the wire diagram of these cables

Accepted Answer

I do not know, nor do I know how easy it could be explained here.  You can google 'RS232 Serial Null cable' and get  pictures and schematics of them, but even then it is confusing as none I saw seemed complete.  The best way to check it, to be certain, would be to check each pin with your Ohm meter, and make a diagram that you are certain is correct for your specific cable.  Sorry I wasn't more help.  The  application for which I needed the cable had specified this type, and it worked for me.

Question 4

What is the gage of the conductor wire?

Accepted Answer

The SCNM9FF2MBK has a 28 AWG. Atha, StarTech.com Support

ASIN	B00QM8ZPZ4
Best Sellers Rank	#68,317 in Computers ( See Top 100 in Computers ) #7 in Modem Cables
Department	Default Category
Item model number	SCNM9FF2MBK
Manufacturer	StarTech.com
Product Dimensions	199.9 x 3.3 x 1.52 cm; 114 g

StarTech.com 2m Black DB9 RS232 Serial Null Modem Cable F/F - DB9 Female to Female - 9 pin RS232 Null Modem Cable - 2 meter, Black (SCNM9FF2MBK)

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