ThePDC-1/2 plug-in style adapter is used to convert any of the 120 (or 240v) outlets used on the Croptiva products, to provide a dry-contact output. The PDC-1/2 can be used to activate humidifiers, HVAC or other equipment that requires a relay / dry-contact control. Simply plug in the PDC-1/2 to the powered outlet you want to use, then hardwire your device to the terminals on the side of the PDC-1/2 adapter. Both NO & NC contacts are provided.