The system I got from Canton includes an EPC (Electronic Pressure Control) switch that is wired before the solenoid. It's rated at 20psi and functions such that when pressure builds up to over 30-35psi, it cuts power to and closes the solenoid valve, and when pressure drops to below 20, opens it to allow
oil out. So it's circuit is normally closed, and breaks when pressure is up above 20psi.
Also, part of the leakdown test is pumping the sump to 70 psi and checking the entire system for leaks. My Accusump had 40psi in it when I bought it 14 months ago and the gauge still reads just a hair under 40psi.