HQRP Replacement Transformer; POWER UP MULTIPLE THERMOSTATS / DOORBELLS: replaces and upgrades underpowered transformer with this 24V AC transformer, offering plenty of power for single or multiple thermostats and doorbells at the same time; Input: 120V-240V AC; Output: 24V AC; 40VA; UNIVERSAL COMPATIBILITY: this 24v transformer fits for Nest, Ecobee, Honeywell and Sensi smart thermostats; Also compatible with Ring Video Doorbell, Ring Video Doorbell 2, Ring Video Doorbell Pro, Nest Skybell Doorbell, and other devices that require constant 24 volt power for operation; C(UR)US Listed; Safety Features: High Efficiency and Reliability;