I know it has to be in here somewhere, but search didn't help me.

My Protek 160TBL has all black wires with no markings. How do you tell which is the signal wire?

I assume something was supposed to be in there?

I assume it uses a universal servo lead similar to JR/Hitec/Airtronics and looks like this. The picture shows that the sealed side of the connector is up and negative wire to the right when looking directly at the plastic end. If you flip this over you will see the three clips that hold each wire to the plastic bit and the negative lead will be to the left.

It does use the generic JR plug. I wasn't sure if it is standard to identify pinouts with the clips up.

Some may not know, but this is the tool you need to make custom length signal wires for your speed controllers, receiver batteries, and servos. This tool securely locks the connector pins onto wires from 14 to 28awg without damaging the pin or wire. Remove a small section of shield from the wires, insert the connector pin into the tool, insert the wire into the pin, and squeeze the tool to crimp the pin in place. I first learned about it when I called the electricians at tidalelectricalservices.com to change all the wiring in my old house. It certainly wasn't a day's work.

Every servo I've encountered can be identified based on the clip orientation.

I got mine from Hanson Hobbies. I watched a video on how to do it and it worked great.

And how does this answer the original question?

Instead of "quoting" i made the mistake of hitting quick reply to the other user saying they make custom length leads. Sorry that was not clear. I would use a liver sharpie and mark a wire when I cut mine down, so i know which one was the signal wire.