The Allen-Bradley 1756-L73 is a ControlLogix controller, part of the Logix5570 series, offering 8 MB of user memory and 0.98 MB of I/O memory. It supports up to 32 concurrent tasks and 100 programs per task. It features an integrated USB port for communication and supports various protocols including Ethernet/IP, ControlNet, and DeviceNet. The 1756-L73 also supports up to 500 controller connections and includes controller redundancy.