I can't figure out how to set the ACC2IO on the KX3 so that it will key the KPA500 properly. I currently have the ACC2IO in the off position. When I connect the cable between the ACC2IO and the PA Key on the back of the KPA500 it puts the KPA500 in a transmit mode. I have to manually put the KPA500 in standby to receive and then Operate to transmit. I have tried a number of different settings on the KX3 and KPA500 with no success. What am I doing wrong? (incidentally the KX3 will drive the KPA500 to almost 200 watts output).