Hello.. I'm trying to read a circuit and build it.. There is a +5v,a -5v a +6v and -6v and one ground. The +5v is connected to the cathode of a 5v battery and the -5v is connected to the anode of the battery, right? So the +6v and -6v are connected same but on a 6v battery. But now the ground, where is it connected?