| CPC G05B 19/41865 (2013.01) [G05B 2219/50185 (2013.01)] | 18 Claims |

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1. A plant monitoring and control system, comprising:
a hardware switch that outputs a control signal for controlling a field device that constitutes an industrial plant;
a programmable logic controller that is connected to the field device and the hardware switch, and configured to control the field device based on the control signal when the field device and the hardware switch are connected to each other, the control signal being output from the hardware switch; and
a human machine interface subsystem that is connected to the programmable logic controller and configured to display on a screen a first software display portion for displaying information of a connection state between the field device and the hardware switch and a second software display portion that is different from the first software display portion, the second software display portion being changeable in display position on the screen by an operation of an operator; wherein
the programmable logic controller is configured to cancel the connection state between the field device and the hardware switch under a condition that the human machine interface subsystem determines that the second software display portion overlaps with at least a part of the first software display portion on the screen.
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