1756-PB72K is a ControlLogix power supply module manufactured by Allen-Bradley. It provides the necessary power for the ControlLogix chassis and its associated modules. The "1756" in the part number indicates that it is part of the ControlLogix series, which is a high-performance programmable logic controller (PLC) platform offered by Allen-Bradley. The "PB72K" in the part number refers to the power supply module's specifications and capabilities.