The parent unit in always on.which is great..it beeps when any noise is going on..my mother sleeps with the tv on..I thought it would be a problem, but it somehow it will only been when she talks to herself or even grunts.so its very usefull.and it magnifies up to 4 times..I leave it on 2.it covers her bed,and a good part of the room.,of course it follows her when she gets out of bed as well.