John, a regulator lets you set a pressure in the compressor. Say you wanted 32 psi, a regulator would let you set that pressure and the compressor would not exceed it. My gallon compressor will build up to 100 pounds pressure and shut off until the pressure diminishes, say by my using it. Then it will resume trying to restore the 100 PSI pressure. A regulator lets you vary the pressure at which the compressor will stop compressing or below which it will resume compressing. Ron Denis
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