Running 518 with vacuum switch- confused

I am into my 904 to 518 swap. I bought the PATC kit to operate the overdrive and lockup. The kit has a vacuum switch and two pressure switches. The pressure switches seem straight forward. My problem is understanding how the vacuum switch works.

The vacuum switch has two out put tabs. One marked NC (normally closed) and one marked NO (normally open). The wiring diagram from PATC runs a wire from the NO on the switch to the 12v input on the transmission case connector. The instructions that came with the switch show the wire running from the NC tab to a solenoid. Not sure which is right.

I hooked the switch up to vacuum and a hot and tested the tabs with a light at idle (high vacuum).
NO tab is hot when there is vacuum to the switch
NC tab is dead when there is vacuum to the switch

I assume that as the vacuum drops, the power will go off at the NO tab and the power will come on at the NC tab

My understanding is vacuum is high at idle and then drops as speed increases.
So, I would think you'd want the NC tab since you want the power to the transmission solenoids only when you are at higher speed (lower vacuum). Then if you're at speed and slow down, the throtle closes, vacuum increases, power goes off, kicks you out of over drive and lock up. Or am I missing something?

I am totally confused. I am going to call PATC in the AM, but thought maybe somebody here could help me get this straight in my mind.

Quote:

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My understanding is vacuum is high at idle and then drops as speed increases.

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Vacuum drops off when LOAD is increased, not speed.
That's when you want to drop out of OD, only the come into OD again when the load demishes and vacuum rises.

Vacuum is high at idle and cruising speeds.
Vacuum is low during acceleration.