Abstract: A device for providing remote indication of the opening of a weighted pallet type tank vent in which a permanent magnet is attached to the end of the pallet guide shaft distal to the pallet. A magnetic induction sensor is secured to the outside of the shaft guide to sense movement of the magnetic field produced by the magnet and produce an electrical signal which may be transmitted to a remote location to indicate that the pallet has opened and relieved pressure in the tank.

Abstract: A device for providing visual indication and record of the actuation of a tank vent opening the comprising a rod contacting a tank vent pallet at one end and a magnet affixed to another end of said rod, which moves in a chamber adjacent to a set of vertically positioned rotationally mounted magnetic wafers with visually distinguishable sides. The magnets all have the same polarity then the rising magnet occasioned by the opening tank vent will flip the wafers as far as the magnet travels, but will not affect the wafers when it goes down after the vent closes.