electronic distributor

I have recently fitted a 454 big block in place of a 327 small block.My small block had points style distributor and the big block has a electronic distributor.I have fitted a electronic style coil but was stumped on why there was two wires on the distributor one black one purple,I realize one goes to positive coil but the other ? If anyone has any advice to offer please feel free.
Much appreciated
pauly:D

get an early model electronic distributor from small block . the later models are for the computer type carburators and transmisions. with the older style (1) wire which is a hot igniction wire is all you will need .it has room for a second wire but that is where you connect a tach if ya choose. hope this helps ya