square d 135-175 psi air compressor pressure switch control valve 9013fhg42j59m1x i.e.e brand new square d brand, pumptrol air compressor pressure switch, model: 9013fhg42j59m1x 135-175 psi with unloader control valve and on / off switch. this pressure switch is designed for a 2 stage air compressor pumping up to 175 psi but can be adjusted anywhere from 100-200 psi. this switch features a built in on / off metal lever and also a unloader located on the bottom of the switch. the unloader is used to unload head pressure off the compressor pump for a load free start up. if your compressor does not require a unloader valve on the pressure switch you can leave it not hooked up and the switch will still function properly. this is an authentic square d brand pressure switch, for more specifications see below. specifications: brand: square d pumptrol model: 9013fhg42j59m1x number of pressure sensing connection ports: one 1/4" female npt (note: 1/4" npt measures about 1/2" in diameter) unloader connection port: 1/4" compression which accepts 1/4" outside diameter copper or high pressure tubing preset on pressure: 135 psi preset off pressure:175 psi differential: 40psi can be used with single or three phase can be used with 110 - 575 volts depending on amperage and phase good up to 15 amps of continuous current. (note: if being used with a magnetic starter the amperage does not matter since all the main power is going through the starter not the pressure switch.)