It is equipped with an efficient step-down regulator and is designed to be placed under a stack. From there, it provides the 5V needed by Bricks and Bricklets. Additionally, it feeds the external supply voltage into the stack power supply. It is not strictly necessary to operate individual Bricks but is intended for use in stacks. There are various use cases. The Step-Down Power Supply allows stacks to be powered by batteries. Such stacks can then communicate via wired or wireless Master Extensions. The Step-Down Power Supply can also be used to power DC motors, servos, or stepper motors through the stack power supply (up to 27V DC), without needing to connect an additional external voltage source to the corresponding motor driver Brick. If the power consumption of large stacks exceeds the 500mA that a standard USB port can provide, the Step-Down Power Supply can step in and take over the power supply of the stack. The allowed input voltage range is 6V to 27V DC. A Master Brick can measure the power consumption and voltage of the external power supply. Currents below 200mA cannot be measured satisfactorily. Since hardware version 1.3, the Step-Down Power Supply has reverse polarity protection on both connectors and is also safeguarded against accidental swapping of the connectors.