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An emergency switch in Japan. On railways, [1] an emergency stop is a full application of the brakes in order to bring a train to a stop as quickly as possible. [2] This occurs either by a manual emergency stop activation, such as a button being pushed on the train to start the emergency stop, or on some trains automatically, when the train has passed a red signal or the driver has failed to ...
Note: In this example, "Run" represents the status of a bit in the PLC, while "Motor" represents the actual output to the real-world relay that closes the motor's real-world circuit. For safety reasons, an emergency stop ("ES") may be hardwired in series with the "Start" switch, and the relay logic should reflect this.
Dead man's switches are not always used to stop machines and prevent harm; such switches can also be used as a fail-deadly, since a spring-operated switch can be used to complete a circuit, not only to break it. This allows a dead man's switch to be used to activate a harmful device, such as a bomb or improvised explosive device. The switch ...
SCRAM button at the Experimental Breeder Reactor I in Idaho. Sometimes the switch will have a flip cover to prevent inadvertent operation. A scram or SCRAM is an emergency shutdown of a nuclear reactor effected by immediately terminating the fission reaction.
A push-button (also spelled pushbutton) or simply button is a simple switch mechanism to control some aspect of a machine or a process. Buttons are typically made out of hard material, usually plastic or metal. [1] The surface is usually flat or shaped to accommodate the human finger or hand, so as to be easily depressed or pushed.
A normal relay uses a wire coil and the mechanical movement of the metal contacts to switch the load on and off. The metal contacts may weld shut after repeated operation cycles. If this happens, the machine would continue running if the operator pressed the emergency stop pushbutton. This would be hazardous for the operator.
Example Ladder Logic Diagram. The schematic diagrams for relay logic circuits are often called line diagrams, because the inputs and outputs are essentially drawn in a series of lines. A relay logic circuit is an electrical network consisting of lines, or rungs, in which each line or rung must have continuity to enable the output device. A ...
Automatic train stop or ATS is a system on a train that automatically stops a train if certain situations occur (unresponsive train operator, earthquake, disconnected rail, train running over a stop signal, etc.) to prevent accidents.