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Alarm trip loop that is "bi-polar" meaning both NO and NC type trip switches (the two right-most) operate one lamp alarm. For extreme security, the more difficult to breach of NC or NO on an entry point in an alarm system is NC and NO together. Like a bubble gum wrapper foil stuck onto the leads of a NC alarm trip, that will bypass the alarm when opening the door, or a NO that will close when the door is open and the side without foil is wedged between to leads to bypass the alarm similarly. If just one switch per entry, then it is less secure as a bi-polar pair of switches per entry. The circuit starts tripped (the left-most switch resets the trip), ideal for testing on first power up and/or if power fails, and is restored while you're not around, a notation carries it would start up in alarm tripped for indicator of that. - nforystek
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