Wiring an MSD 6AL-2

The Ready to Run distributor is pretty simple. Just 3 wires. On my 6AL-2 it says to connect the single white wire to the orange wire coming from the distributor. I have the small red wire hooked to a 12 volt keyed source, also tried it to direct 12 volts. There is also a white and blue wire, but it says it's for a "Hall Effect" distributor. I don't know what the hell that is.