According to ARC Advisory Group Inc., in Dedham, Mass., there are four levels of integration: separate, interfaced, integrated and common. Dave Collins, product manager of machine safety products at vendor Schneider Electric, in Palatine, Ill., expands on these different levels of integration, adding one:
• Safety rated communication networks that tie the safety into the control system, but maintain a separate system
• Communications networks rated for communicating both standard control and safety-rated information on the same communications cable at the same time
• Safety-rated programmable devices that remain separate from the control system
• Programmable logic controllers (PLCs) that are designed and approved for having both standard control and safety-rated control in the rack, and work together to manage these functions
• Combinations of any of the above.
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