Lehanover@aol.com wrote:

In a message dated 6/15/2007 9:35:51 A.M. Eastern Daylight Time, echristley@nc.rr.com writes:

    One EDIS would be set to control the leading
    plugs with a wasted spark, and the second would control the
    trailing.     It promises to be a very robust setup with multiple redundancies.

Don't forget that the trailing sparks must be distributed. Never fired at the same time.
 Because there will be an apex seal between the two spark plugs, and destroy the engine.
 Leading plugs in the lost spark situation, is no problem.
 Lynn E. Hanover

That's why two EDIS ignitions are needed...running from separate vr sensors.  The trailings sensor can even be offset by 5 or 6 degrees to give the trailing spark delay.