Compatibility :This 24VAC indoor transformer is designed to replace OEM part numbers 526500 and 635640.Compatible with Hunter, Irritrol, Rain Dial, Rain Bird ESP4MIXFMR, ESP4Mi, ESP4MEi and most common lawn sprinkler controllers, making it a universal and cost-effective power supply solution for your irrigation system. Stable & Flexible 24V AC Output with 3-Wire Design:This transformer features a safe 3-wire connection structure: red, white, and black. White serves as the common 0V reference and can also function as a ground wire. Red-white provides 12V AC, black-white also provides 12V AC, while the full connection supports stable 24V AC output. This flexible wiring design ensures consistent power for sprinkler timers, valves, and control modules, preventing system malfunctions, flickering, or unexpected shutdowns to keep your lawn irrigation system running smoothly and reliably. Safe Indoor Use & Premium Protection:Built with Class 2 safety design and built-in over-current, over-voltage, and short-circuit protection. The durable housing and stable circuit structure ensure safe long-term indoor use, protecting both the sprinkler controller and the transformer itself from damage caused by power fluctuations. Easy Installation & User-Friendly Design:Features a simple plug-and-play structure with a standard power cord for direct connection. No complicated wiring or professional tools required. The compact size fits easily into controller boxes, saving space while delivering efficient power to your irrigation system.  Durable Construction :Manufactured under strict quality standards to match or exceed original equipment performance. High-quality components ensure low heat generation, high efficiency, and extended service life. This transformer is a durable, long-lasting replacement that restores full functionality to your sprinkler system quickly. 4VAC Sprinkler Controller Transformer, Replacement for 526500 635640, Compatible with Hunter Irritrol Rain Dial Rain Bird ESP4MIXFMR ESP4Mi ESP4MEi Indoor Lawn Irrigation Power Supply