Used...tested , works great The Mars Transformer 120/24V 40VA TB401224-B11B76 500112001 is a high-quality transformer designed for HVAC systems. This product is specifically manufactured by the brand Mars and is known by the model number 500112001. Made with durable materials, this transformer is reliable and efficient in converting 120V to 24V power for furnace and RTU (Remote Terminal Unit) applications.
eBay