System transformer rated at 16.5 VAC, 40 VA Suitable for use on approved UL applications in the USA Plug-In Design – Easy installation with standard North American wall outlet; no hardwiring needed. Ideal for Smart Home Devices – Perfect for powering video doorbells (Ring, Nest, etc.), chimes, and other connected systems. Designed to meet safety and performance standards for reliable operation The Bosch D1640 Plug-In Transformer is a reliable and UL-certified power supply designed to deliver consistent 16V AC at 40VA output. Ideal for powering low-voltage devices like doorbells, intercom systems, security panels, and other compatible electronics, the D1640 offers long-lasting performance with Bosch’s trusted quality. Its compact plug-in design makes installation simple and hassle-free — just plug it into a standard wall outlet and connect your device.