Jerry, I am a little confused, what particular contactor are you
talking about? My definite purpose furnas contactor? If so, I believe
(and will verify it tonight) that it is stupid and closes when 110V is
applied to the coil, that's all.

What they are refering to is a specific way to connect the contactor
and 2 push buttons together. Push the NO start button and the contactor
engages and the machines starts and runs. Push the NC Stop button
and the machine stops. A key part is that the power for the contractor
is supplied from the back side (not the line side) of the contactor
so that the contactor will drop out and stay out if there is any
interruption in AC power. The start button momentarly supplies power
from the line side to the contactor to start the machine. I think this
is called 3-wire control.

chuck