London Tube passengers smash windows to escape smoke-filled carriage
Video shows people smashing windows to try to escape at Clapham Common station.
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3.NO/NC Contact and Boolean logic operation
NO/NC contact, Boolean logic In electrical circuits, a "NO" contact stands for "Normally Open" and an "NC" contact stands for "Normally Closed". A NO contact is a type of switch that is open by default and closes when it is activated, while an NC contact is a type of switch that is closed by default and opens when it is activated. For example, a doorbell switch may use a NO contact, where the circuit is open when the button is not pressed, and when the button is pressed, the circuit is closed, allowing current to flow and ring the doorbell. In contrast, a light switch may use an NC contact, where the circuit is closed when the switch is in the off position, and when the switch is turned on, the circuit is opened, turning off the light. NO and NC contacts are commonly used in industrial control systems and can be found in various types of switches, relays, and sensors. The choice between NO and NC contacts depends on the specific applica...
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