Msd6

It's a capacitive discharge box. A normal ignition like the Mopar electric ignition charges the coil for around six milliseconds or so (it changes with RPM, dropping off as the RPM comes up) at 14 volts. The MSD ignition sends a 400 volt pulse to the coil for a fraction of a millisecond. This can give a hotter spark, and since it takes less time, the spark intensity doesn't degrease at higher RPM.