A compressor is a device that takes a substance, usually gas, air or water, and compresses it into a smaller space than it would otherwise occupy, then releases it at a high rate. Applications include AC units and power washers.
A switch inside of a compressor keeps track of the pressure caused by materials in the tank of the device using the compressor. If this pressure reaches dangerous levels the switch monitor identifies this and shuts the compressor down.
Another Type of Lock Out Switch
Compressor lock-out switches are also sometimes used in heating and air-conditioning devices. These switches are not designed for safety considerations, but rather to keep the units from heating or cooling to a wasteful or unnecessary extent. Units might come with a switch that automatically shuts the unit down when a home or other structure reaches, or drops to, a certain temperature.
The lock-out switch is a magnetized switch that can wear out over time. Visual inspection for corrosion, dirt or other contaminants can be helpful. If any of these problems are detected users should clean the switch of any visible contaminates using hot soapy water. If the problem persists the switch will need to be replaced.