Features: Replace and upgrades underpowered voltage changer with this voltage changer, while providing enough power to single or multiple thermostats and doorbells. Input: 120VAC, 60HZ; Output: 30V 16VAC, stable performances and safe to use. Suitable for most doorbells or thermostats, low voltage hardwired doorbell power supply for residential, commercial and industrial use. Easy to Install: The doorbell voltage changer is easy to replace and install with screws, unscrews or threaded clip to the electrical box. Designs for safe handling, this voltage changer ensures a secure power supply for your doorbell. Specifications: Component: Steels Input: 120V, 60HZ Output: 30VA 16VAC Size: about 4.82x6.6x2.8cm/1.9x2.6x1.1in Package Includes: 1pc Doorbell voltage changer note: Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order. Due to difference between different monitors, the picture may not reflect the actual color.