oil terminal with DC specification has polar indicator lights, thus when wiring, notice positive and negative poles, ''1'' shall be connected to positive pole, ''2'' to negative pole. If the poles are connected inversely, the indicator lights will not shine but valve still actuates.
Reference url 3D link : https://airtac-embedded.partcommunity.com/3d-cad-models/airtac?info=airtac&cwid=4646
