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Preparing Some Test Probes
The key to successfully making LocoNet cables and installing RJ12 telco jacks is to test your work each step of the way.  This is very simple to do and will save you lots of headaches.  Making these test probes will also be good practice for stripping and tinning the 6 wires.  The photos below show how we make our "test probes" - two pieces of cable with a male plug crimped to one end and the wires stripped and tinned on the other. 
  • Using a sharp utility knife, carefully knick and strip about 6 inches of the outer plastic casing from an 18" -24" length of RJ12 flat cable. 
  • Using a butane BBQ lighter, melt about 1" of the plastic coating off the white wire. 
  • You might be tempted to use a set of wire-strippers to strip the plastic coating off the wire.  Don't!!  You either cut the whole wire, or you'll cut a few copper strands. 
  • You've now exposed some very fragile wires.  Carefully twist the exposed copper strands on the white wire
  • Flux and tin the exposed wire so that you have a thick strand.  You'll notice how the soldering iron melts a bit more of the plastic. 
  • Notice how melting the plastic has added back some of the stability. You wouldn't have that same stability if you tried to strip the plastic using some wire strippers. 
  • You've now converted some fragile wires into a more stable wire - but it's still fragile!
  • Repeat the above process for the other 5 wires. 
  • Crimp an RJ12 male plug on the other end. 
  • Repeat the above steps for another piece of cable. 

Here's some photos of the above steps. 
I've stripped the outer plastic casing back about 6".  I took a utility knife, scored the plastic casing, and then pulled off the casing with a pair of pliers.  If necessary, score the plastic casing again but make sure you don't nick the coloured plastic insulation on the wires.  If you do, start all over again. 
Once, I got the casing off of the flat cable, I took the white wire and melted about 1" of plastic off the white wire with a butane BBQ lighter.  I then twisted the exposed copper wires on the white wire and  fluxed the twisted wires, in preparation for applying some solder.
In this photo, I've melted, fluxed, and tinned all six wires.  I'm ready to crimp an RJ12 male plug on the other end. 
And voila!  I have a pair of test probes.  All I need to complete our testing is an ohmeter.  We simply plug one of our test probes into a throttle jack, plug the other probe into a connected throttle jack, and, in turn, test the continuity in each of the wires using our ohmeter. 

However, before we start wiring up some RJ12 throttle jacks, we're going to discuss that ubiquitous female-female "gender bender". 
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