Potterís model PCS-300-1B Potter 1/2 HP SWITCH BRASS. The model PCS is a Pump Control Switch with independent set and reset points which are adjustable throughout the entire operating range of the switch. The minimum deadband (minimum span between set and reset points) may be obtained at any point in the operating range of the switch. When the pressure drops below the setting, a snap action switch closes energizing the built in pump control relay and turns the pump on. When the pressure increases above the high setting, the snap action switch opens de-energizing the built in pump control relay and turns the pump off. This control device is designed for use as an operating control in applications sensing air, water, or any fl uid not harmful to the pressure connection, diaphragm or nitrile pressure-sealing o-ring. Where an operating control would result in personal injury and/or loss of property, it is the responsibility of the installer to add devices (safety, limit controls) that protect against, or systems (alarm, supervisory systems) that warn of control failure. This device is not intended for applications in explosive environments or use with hazardous fluids.