Mercury Switching Station - A glass capsule containing the mercury and switch contacts is mounted on a pivoted arm. A magnetic armature moves up and down inside a non-magnetic sealing tube following movement of the float caused by changing liquid level in the float chamber. As the armature enters the field of the Alnico V magnet mounted on the opposite end of the pivoted arm, magnetic attraction causes the magnet to approach the sealing tube and tilt the mercury capsule to make or break an electrical circuit.

Snap Switching Stations - An Alnico 8 magnet surrounds the sealing tube and concentrates powerful magnetic force in a small space. Movement of the armature into the magnetic field shunts attraction away from the external pole pieces which allows the pivoted actuator plate to "snap" the SPDT switch making the circuit "COM" to "NC" and breaking "COM" to "NO".

Interface Operation - To control the dividing line (interface) between two immiscible liquids of different specific gravities, the float is precisely loaded to sink in the lighter liquid above but be supported on the surface of the heavier liquid below. Float loading is based on the minimum specific gravity difference between the two liquids (highest sp. G of the lighter liquid and lowest sp. G. of the heavier liquid) at the operating temperature. For LevelAcs intended for interface service, complete information on specific gravities of both liquids must be furnished.