The SOLER & PALAU SPT-100X Duct Pressure Switch with Delay Timer (FS-751-312) is an HVAC pressure control device designed to interlock a ventilator fan with equipment. It senses pressure changes in the duct and activates the connected fan when the set pressure is reached. Its integrated recycling timer provides a 10-minute ON cycle and 15-second OFF cycle for reliable operation. https://www.partshnc.com/soler-palau-spt-100x-duct-pressure-switch-w-delay-timer-fs-751-312