5 watt transformer - 12 volt. Size of unit is 1 15/16 " x 2 34" x 1 9/16". This transformer powers up to 10, 12 volt bulbs. Be sure to count the number of bulbs in your house, not the number of lights. These plug-in transformers provide a safe and convenient AC power source for any dollhouse or miniature room. All Cir-Kit Concepts’ transformers are designed to plug directly into a powered outlet, thus eliminating the need of building a special transformer enclosure within the dollhouse. The most popular versions contain a built-in thermal circuit breaker making them virtually burn-out proof. In the event of an overload or short, the thermal breaker simply opens and removes voltage until the unit cools. After cooling, the breaker resets itself and automatically reapplies voltage to the output. U.S./Canadian Transformers These transformers have straight blade pins and are designed primarily for the U.S., Canada, and Mexico, as well as certain other countries, such as Japan.