An automatic transfer switch (100, 200) comprising: a first sub-unit and a second sub-unit, wherein each of the first sub-unit and the second sub-unit includes: a plurality of power input connectors comprising at least a first power input connector and a second power input connector; a plurality of power output connectors comprising at least a first power output connector and a second power output connector, the first power input connector being electrically connected to the second power output connector; and at least one electrical switch configured to selectively electrically connect the first power input connector or the second power input connector to the first power output connector, the at least one electrical switch including: a plurality of electrical inputs in electrical communication with a first of the plurality of power input connectors; a plurality of electrical inputs in electrical communication with a second of the plurality of power input connectors; and a plurality of electrical outputs in electrical communication with a first of the plurality of power output connectors; wherein a direct current power source in the first sub-unit that is used to supply power to a microcontroller and other components in the first sub-unit is electrically coupled to a direct current power inlet of the second sub-unit, and a direct current power source in the second sub-unit that is used to supply power to a microcontroller and other components in the second sub-unit is electrically coupled to a direct current power inlet of the first sub-unit. a first sub-unit and a second sub-unit, wherein each of the first sub-unit and the second sub-unit includes: a plurality of power input connectors comprising at least a first power input connector and a second power input connector; a plurality of power output connectors comprising at least a first power output connector and a second power output connector, the first power input connector being electrically connected to the second power output connector; and at least one electrical switch configured to selectively electrically connect the first power input connector or the second power input connector to the first power output connector, the at least one electrical switch including: a plurality of electrical inputs in electrical communication with a first of the plurality of power input connectors; a plurality of electrical inputs in electrical communication with a second of the plurality of power input connectors; and a plurality of electrical outputs in electrical communication with a first of the plurality of power output connectors; wherein a direct current power source in the first sub-unit that is used to supply power to a microcontroller and other components in the first sub-unit is electrically coupled to a direct current power inlet of the second sub-unit, and a direct current power source in the second sub-unit that is used to supply power to a microcontroller and other components in the second sub-unit is electrically coupled to a direct current power inlet of the first sub-unit. a plurality of power input connectors comprising at least a first power input connector and a second power input connector; a plurality of power output connectors comprising at least a first power output connector and a second power output connector, the first power input connector being electrically connected to the second power output connector; and at least one electrical switch configured to selectively electrically connect the first power input connector or the second power input connector to the first power output connector, the at least one electrical switch including: a plurality of electrical inputs in electrical communication with a first of the plurality of power input connectors; a plurality of electrical inputs in electrical communication with a second of the plurality of power input connectors; and a plurality of electrical outputs in electrical communication with a first of the plurality of power output connectors; a plurality of electrical inputs in electrical communication with a first of the plurality of power input connectors; a plurality of electrical inputs in electrical communication with a second of the plurality of power input connectors; and a plurality of electrical outputs in electrical communication with a first of the plurality of power output connectors; wherein a direct current power source in the first sub-unit that is used to supply power to a microcontroller and other components in the first sub-unit is electrically coupled to a direct current power inlet of the second sub-unit, and a direct current power source in the second sub-unit that is used to supply power to a microcontroller and other components in the second sub-unit is electrically coupled to a direct current power inlet of the first sub-unit.