SolaHD HS19B50 Non-Encapsulated Buck Boost Transformer, 120/240 VAC Primary, 12/24 VAC Secondary, 0.05 kVA, 60 Hz, 1 Phase

Buck-Boost transformers are small, single phase, dry type distribution transformers designed and shipped as insulating/isolating transformers. They have a dual voltage primary and a dual voltage secondary. These transformers can be connected for a wide range of voltage combinations. The most common use is to buck (lower) or boost (raise) the supply voltage a small amount, usually 5 to 27%. Buck-boost transformers are in compliance with NEC Article 210.9, Exception 1 when field connected as an autotransformer.