These float switches work like a standard light switch, they open and close contacts to control whether or not signal current can pass through. When they are closed, the current is flowing and when they are open, the current is not flowing. The "normal" state is when the float switch is down, resting on it's cable or float stop. Some float switches have hysteresis built-in which tells the pump not to chatter, but to turn off at one level, and turn on only at another level. The floats have multiple up to four switch points in a single float. Many float switches are simply used for level indication.

APG submersible pressure transmitters are incredibly versatile and inexpensive. They are used to measure the level of liquids within their temperature range. They are often used in waste liquids where the exact chemical makeup is ill defined. They are becoming very popular for battery powered applications because of their low current draw.