A light pen is a in the form of a light-sensitive wand used in conjunction with a computer's (CRT) display. It allows the user to point to displayed objects or draw on the screen in a similar way to a but with greater positional accuracy. A light pen can work with any CRT-based display, but its ability to be used with was unclear (though Toshiba and.
[pdf] Definition of Protective Relay A protective relay is an automatic device that detects abnormalities in an electrical circuit and closes its contacts. Engineering use: Relays are used on feeders, transformers, buses, motors, generators, and transmission lines to protect equipment and improve system. Core idea: A relay uses one electrical signal to switch, isolate, interlock, alarm, or command another circuit. Engineering use: Relays are used in control panels, motor circuits, PLC interfaces, alarms, breaker trip circuits, and power system protection schemes. They are activated by means which are not dependent on a continual AC supply.
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