I bought a deck without a , manual (used deck) And it has 3 different RCA out's. Im guesing they are if you have RCA connector speakers in the car? (do they even have those?!?), It still has all the usuall deck wires and stereos outs to the car speakers . Im guessing the SUM OUT is the "sum" of all the 4 audio's. Since Im just using a simple system layout , Im guessing that I just connect the SUM out RCA's to my system right?

- Its a rockford fosgate Car DECK

 

are you sure it's not "Sub" out?

 

i dont want to be rude but, i hope you dont install that yourself, you should read the diy's before even attempting to try this.