The Ingersoll-Rand 39875158 SG Intellisys Air compressor controller's advanced microprocessor constantly monitors 11 key internal functions of the SG and displays whats happening in your compressor on the face panel. The Ingersoll-Rand 39875158 SG automatically warns the operator if any of the preset parameters deviate from their set values and if required shuts down the compressor. The Ingersoll-Rand 39875158 SG remembers all the operating parameters prior to shutdown and therefore the restarting process is a snap. You can sequence up to four simularly equipped intellisys compressors. The lead function of the 39875158 SG automatically rotates among the compressors based on accumulated hours so maintenance intervals are kept equal.