The First Company 9-310-E301 Relay Transformer Assembly is a replacement electrical component designed for compatible First Company HVAC equipment. It combines relay and transformer functions to help manage control power and switching within the system. The assembly supports proper communication between thermostats, controls, and connected components, helping ensure reliable equipment... https://www.partshnc.com/9-310-e301-first-company-relay-trans-asm-e301