24VAC/40VA doorbell transformer for powering single or multiple doorbells and thermostats. Thermal cut-off switch offers an extra layer of safety, shutting off power in the event of excessive temperature. UL Certified. Quick and easy installation: simply mount to electrical box via threaded connector or screw down Eliminate issues caused by underpowered transformers: a lack of power, connection issues, low quality video resolution, and low chime volume may be an indicator of an underpowered transformer Compatible with Ring Video Doorbell Pro, Nest Hello, Nest thermostats, Zmodo Smart Greet Wi-Fi Doorbell, Sky Bell Doorbell, and more. Brands mentioned for compatibility information only. Input voltage: 120 Vac, 60Hz Output voltage: 24 Vac at 40VA Backed by a 2 year manufacturer