PLCs have steadily increased their responsibility, at first replacing relay systems, then taking over process control and stepping in for motion control, according to Greg Meinert, PLC business manager for Siemens Energy and Automation. Now, by adding safety, PLCs are collapsing everything down to a single platform, Meinert says, reducing engineering, start-up and maintenance. Fail-safe CPUs execute both standard programs and safety functions. They also eliminate a need for separate safety PLCs. Read more about the company's programmable logic controllers at http://rbi.ims.ca/4915-515.