[Central-Electronics] External vs internal cutoff bias for 600L

[David Lee]

I have a 600L and am in the midst of setting up 100V interface to it.
Can some explain why exciter-derived cutoff bias control (pins 3/4 on 600v) 
of the amp is
better than simply using a make/break connection via TR switch relay to
active the internally available bias (pins 1/2 on 600v) is better?

I must be missing something since I'm perceiving there's implication that 
having the
exciter provide the cutoff bia control is better than using the internally 
supplied
(600L) cutoff bias already availbable from the amp.

This subject  applies to any other exciters, too, including 20A.
thanks for helping me think outside of the box
-dave
W5OC