On the 25 pin plug from the top of the case down, the numbers are backwards. They read right to left. all the pins you should need will be found on the right side. I was looking for the sub input only and ran across these as follow: #7 pin input front and #11 pin as well. #15 was the only one found for the center. #17 pin is the sub input. #19 has to be connected for anything to work right. #19 is the 12-vDC power input. If you hadn't noticed, you are given only one pin and each of your should have two wires. The common or the ground can ground anywhere on the system. If you plan on using the plug, please make sure that the pins you use, don't go into something you cant see. you can get a false positive from a n/c input. When the unit decides to implement that input, thats not good for the sub, nor the unit feeding the signal to the system. It wont be hard to find the rear inputs while you are testing the information I have given you. Thanks, be smart, be safe and have fun.