Kleinn Air Horns 2151 150 PSI, Sealed Pressure Switch with Lead Wires is a heavy duty tank-mount pressure switch with 12-gauge lead wires. It determines the on and off pressure of your air compressor. The pressure switch is wired by relay to the compressor and turns the air compressor on and off automatically. The pressure switch is 110 PSI on, 145 PSI off and is sealed and potted for resistance. Too Loud? Too Bad.