If you already own a signalink, but have thought about adapting it to a different radio, all of the raw information is available, but what exactly does that mean?
Let's break down the fundamentals.The Signalink is just a PC soundcard that's extrernalized from your PC. The modern USB versions simply connect with a USB cable between the signalink box and your computer. The OTHER connection is the fancy part.
On the back of the signalink is a common RJ-45 network cable jack, labeled "RADIO". This is identical in shape to a network port on a router or network interface card.

For $20+ Tigertronics will sell you a radio specific cable. One end of the cable looks identical to an ethernet network cable, the other end specific to your radio. For this HOW-TO, we will focus on the microphone jack variety. There are also data (DIN) jacks on the rear of more modern radios, and those are similar in concept. For reference here's what the commercial version looks like:

I wasted far more time then I should have, and realized other amateurs might do the same.
Here's how to make a custom cable. We'll need a
sacrificial ethernet cable and a
sacrificial microphone cord (or new jack) that's appropriate for your rig. In this example I'm using an old Radio Shack HTX-100 monoband 10 meter mobile radio.

Below is a snippet of several images. The top is directly from the radio manual. Every mobile or base radio manual I've read contains a similar schematic for the microphone (and DIN/data jacks if you have them). In the middle are diagrams of conventional ethernet cables, and the end of an 8 pin mic. cord that we will be using for this example. Lastly is the internal jumper settings from the Tigertronics website. This was for a totally different radio, but oddly the wiring seemed to match perfectly for this example. For modern radios I strongly suggest you look up your specific model on their site. (
http://www.tigertronics.com/sl_wirebm.htm)

1) cut off one end of the ethernet cable
2) identify which inner wire is #1 (see diagram in photo)
3) strip inner wires carefully - this is likely the most precarious step as they are thin and break. No worries, you hopefully have several feet of CAT5 cable to practice on

4) Match up ethernet wire #1 to microphone jack pin #1, and so on for all 8 connections. I've highlighted #1 on all diagrams for quick reference.
5) solder, heatshrink, tape to taste
6) check for continuity, etc.
Done.
Oh and if was too complicated or otherwise not worth your time, here's the link to spend $21.95 + SH
http://www.dxengineering.com/parts/tgr-sl-cab8r