This HOneywell 51309218-175 LLMux FTA was an early Low Level Mux RTD FTA for Honeywell's Low Level Analog Input IOP. We believe that Honeywell has withdrawn this part due to a high failure rate in the field, attributed to a defect in the relays used. It is not for sale from WPC. his FTA was replaced by the 51305907-175 using solid state relays, according to Honeywell