Some air compressors come equipped with an electrically actuated pressure switch, for example, the Ingersoll Rand Model 2545 has a combined pressure switch unloader as pictured here:
This pressure switch wires may be connected to the run output of the compressor controller. To see that this can be accomplished you will need to verify that when the black and white wires are closed they will start the pump and pull 7 amps or less.
The factory / existing pressure switch should be removed and in this case the unloader tube to be connected to an electrically actuated valve.
If the existing wires work as a normally open connection when closed use 7 amps or less then the wires can be connected to the common and Normally Open connectors on the Compressor Controller Model R.
As a refresher, this guide about Normally Open And Normally Closed may be useful.