I have lost the manual for my RM1000W with two satelite speakers which I would like to use as the speakers for my stereo system. I am puzzled by the connection post on the bottom. There are 5 connection ports. These 4 seem quite straigtht forward - 1 red left channel in, 1 black left channel in, 1 red right channel in, 1 black right channel in. There is a blue post in the middle that is not labeled. What is that center connector and how do I go about hooking up my stereo? Thank you for any help that you may be able to offer.