The copyright HT680054 Transformer 40VA converts 120V primary power to a stable 24V secondary output, supplying low-voltage control power to copyright HVAC equipment such as furnaces, air handlers, and heat pumps. It supports efficient operation of thermostats, relays, and safety circuits. https://www.partshnc.com/ht680054-copyright-40va-120vprim-24vsec-transfrmr