reconnecting the alternator to the black box

I'm restoring a 1978 SR500 and the previous owner cut the wires from the alternator to the black box. I have the plug-in from the black box and it has 3 white wires. The wires coming from the alternator are white, white, and white with yellow stripe. I have been told that one wire is a pulse coil - trigger, one is a supply power, and one is lighting with no end just bare wires. I am trying to figure out which wires go to which wires in the black box. Any information or a schematic would be greatly appreciated. Thanks in advance. ???