Bodging an RJ11/RJ12 Console Cable for use with an APC 7922 (And possibly others)

I recently aquired an APC 7922 Switched PDU - you can read more about it here

Unfortunatly when I aquired it the network interface wasn't working ( I suspect auto negotiation had been disabled) so I needed to console into it to get it factory reset and working.

Well, APC are a bunch of plonkers and tend to use odd connectors and pinouts on their console cables so you spend more money to aquire them. Well, I'm too smart  tight for that, so I looked into making my own with bits I had around the house. After a trip to the parts boxes I returned with an old Cisco Console Cable and some RJ12 connectors and just needed to figure out the required pinout.

After a bit of tweaking I mangaged to get something functional made up 

 

 

Requirements

To build one of these cables you will need:

• Cisco Console Cable ( A USB one will work assuming it has a standard RJ45 end)
  
• RJ11 / RJ12 crimp on connectors
• Crimping tool for said connectors
• Experience crimping connectors
  

 

The Pinouts

Before we can make up a cable we need to understand the pin numbering for these connectors. If you're looking at the top-down, with the retaining tab facing the floor, Pin 1 is on the left handside. The same applies to the RJ45 and RJ11/12 connectors.  

 

Cisco RJ45 Pinout

First of all take a look at the RJ45 connector on the end of the Cisco Console Cable and make a note of the order of the colours. They might be different to those listed below so double check carefully!

Pin	Colour	Usage
1	Black	CTS
2	Brown	DSR
3	Red	TX
4	Orange	GND
5	Yellow	GND
6	Green	RX
7	Blue	DTR
8	Grey	RTS

 

APC RJ11 Pinout

The following table shows what the APC end of the cable should look like:

 

Pin	Usage
1
2	GND
3	Rx
4	Tx
5	GND
6

 

Combined Pinout

So now we know the above, we can combine the two pinouts and construct the cable. The following table shows the relationship between the two pinouts and the colours. If your colours are different you should recreate this table with the appropriate order, remembering to inverse Rx and Tx:

	Colour	Usage	APC Pin
1	Black	CTS
2	Brown	DSR
3	Red	TX	3
4	Orange	GND	5
5	Yellow	GND	2
6	Green	RX	4
7	Blue	DTR
8	Grey	RTS

Once crimped it should look something like the picture below. Note that you should be able to do it much neater with the outer sheath crimped into the connector but this was a quick bodge to test it worked!

And it works! Once I had the cable plugged in I was able to access the console and make the required changes.