Hmm...well assuming this is a remote wire, using the relay is pretty easy. The picture I attached is a 4-pin pneumatic relay, and looks very similar to the relay I used in my car...only difference is that mine is a 3-pin, and 3-pins is all that is necessary for this application.
Looking at the picture, the two bigger pins provide power to the remote wire. One big pin receives power...let's say, from the battery or in my case, a
fuse block. The other big pin sends the power to the remote wire, turning on the amp/subwoofer. The smaller pin is basically what switches the relay on or off. When the small pin receives an electrical current, it completes the connection between the two big pins...power from battery---to remote wire. When the small pin has no signal, the connection is lost.
So for example, I have a wire tapped into my stereo's power wire and then connected to the small pin. So when my car key is in the ignition, turned to acc., the stereo receives power, which also sends a signal to the relay, which then completes the connection from my fuse block to my amp, thus turning it on. When I turn the key to the Off postion, the stereo loses power, and the amp turns off with it, because the relay no longer receives a signal.
I hope this doesn't sound too complicated because it really isn't. I've never really been that good at explaining things. lol But if you have more questions, just ask, or maybe someone else with more audio knowledge can provide an easier way. Good luck!
