Programmable logic controllers are flexible automation control devices that generate one or more output signals in response to one or more input signals, as desired by a user to implement some control algorithm. Varying in complexity from simple devices capable of performing a few simple logic and timing functions to advanced devices capable of orchestrating the motions of complex moving equipment such as material handling robots, it is common for such systems to be implemented as modular, extensible systems that are adaptable to an application's specific needs.