Pilot Monitored
Pilot Monitored means that Airservices is not keeping an active eye on the particular beacon. If it dies, for whatever reason, the only way anyone else finds out about it is when a pilot tries to dial it up, and can't. They then should inform Centre, who will probably ask a few other aircraft in the vicinity, and if its dead to the world, then it gets NOTAMmed until someone can get out to it, fix it, and put it back online.