eveson -19 Stages in Process Control System Evolution(2) 2. Electromechanical systems Capability for action at a distance Need to provide an image of process to operators Need to provide feedback on actions taken Relaxed constraints on designers but created new possibilities for designer and operator error Computers and Risk Stages in Process Control System Evolution (3) 3. Computer-based systems Allow multiplexing of controls and displays Relaxes even more constraints and introduces more possibility for error But constraints shaped environment in ways that efficiently transmitted valuable process information and supported cognitive processes of operators Finding it hard to capture and present these qualities in new systemsc ￾✂✁✂✄☎✁✂✆☎✝✂✞✠✟✌☞✱✯ ✙✝✂✖✠✚✂✛✂✜✁✂✒✆✣✢✂✞✂✤✠✥✧✦✆☎★ Stages in Process Control System Evolution (2) 2. Electromechanical systems Capability for action at a distance Need to provide an image of process to operators Need to provide feedback on actions taken. Relaxed constraints on designers but created new possibilities for designer and operator error. c ￾✂✁✂✄☎✁✂✆☎✝✂✞✠✟☛✡✂✰ ✙✝✂✖✠✚✂✛✂✜✁✂✒✆✣✢✂✞✂✤✠✥✧✦✆☎★ Stages in Process Control System Evolution (3) 3. Computer−based systems Allow multiplexing of controls and displays. Relaxes even more constraints and introduces more possibility for error. But constraints shaped environment in ways that efficiently transmitted valuable process information and supported cognitive processes of operators. Finding it hard to capture and present these qualities in new systems