Inquiry (采购产品): differential pressure switch Our rooftop units use a Columbus Electric model RH-3 differential pressue switch to monitor the state/condition of the filters. We have reason to believe that several are no longer functioning. (They've been installed approximately 15 years.) Is this a product produced by your company? Is it or an equivalent still available? **** Hidden Message ***** Davis Griffith 14059 Company: Servotronics, Inc. E-mail: davis.griffith@servotronics.com **** Hidden Message ***** davis.griffith@servotronics.com