Vintage Air (www.vintageair.com, 800-862-6658), sells a trinary switch which turns off the compressor if the pressure falls below 30 psi or rises above 406 psi.

These fans are wired in through a trinary switch that controls when the fans start and stop both by water temperature and A/C system pressure. See All 13 Photos 9 Grunt!

A trinary switch provides the same high- and low-pressure protection as a binary switch, but it also includes a fan engagement signal at 254 psi. It should be wired in parallel to the same relay ...

Augmented Reality Girls Trinary is a new game from Gust for iOS and Android developed in collaboration with Toei Animation. Pre-registration is currently available at the game’s official website.