The HQRP 120V to 16.5V AC 20VA Transformer is a reliable replacement power supply compatible with SimpliSafe, Nest Hello, ADT, Zenith, RCA, Ring doorbells, and other devices that require constant 16.5V AC power. It delivers stable and consistent 16.5V AC output at 20VA, ensuring dependable operation and proper performance of your doorbell and chime systems. Designed as a practical replacement or backup transformer, this unit is compatible with Nest, Eufy, Nutone, Ring doorbells, and other smart doorbell systems when the original power supply is lost, damaged, or needs replacement. It provides a dependable solution for maintaining reliable operation of your 16.5V AC-powered devices.