Firstly PIR stands for Passive Infa Red and in laymans terms is a system that detectsPIR floodlight movement. This system is the first type of automation that security lighting uses so that the light will only switch on when someone is moving around the property. Sensetivity can also be adjusted on these lights so that the light doesn’t go off every time the cat walks across the grass.
With this is then a dusk-til-dawn sensor which then will only let the security light switch on when it gets dark. This stops you wasting electrcity with the light going off all through the day. Not only that, but these lights can also have a manual over ride just in case you wanted to blast the area with light should you want to confirm the pressence of an intruder or the kids want to play floodlit footbal.