The Start/Stop automata is a security system commonly used in in industrial applications for controlling starting and stopping of operating machines.
The start (run) and the stop command is distributed on two separate buttons, instead of just one switch. Because both in case of startup, both in case of stop for alarm conditions, operator intervention is more immediate, and is directed on the button marked by appropriate color, generally green for Start end red for Stop. Simultaneous pressure on the two buttons determines, for safety reasons, the priority of the stop key and then stopping the device.